DETAILED DESCRIPTION OF THE INVENTION

[0028] The present invention provides a method of treating an infection caused by bacterial cells located on a surface of a foreign body over and around which fibrin has been deposited, the foreign body being present in a subject, which comprises administering to the subject an agent capable of inhibiting signalling mediated by a β₁ integrin cell surface receptor of leukocyte cells in an amount effective to enhance the migration of leukocyte cells into or through the fibrin so as to permit the leukocyte cells to reach and kill the bacterial cells and thereby treat the infection.

[0029] In one embodiment of the invention, the foreign body is a prosthetic device, a catheter, or a suture.

[0030] In another embodiment of the invention, the subject is a mammal such as a human.

[0031] In yet another embodiment of the invention, the leukocyte cells are polymorphonuclear leukocyte cells such as neutrophils, basophils, and eosinophils.

[0032] In another embodiment of the invention, the leukocyte cells are monocytes or macrophages.

[0033] In yet another embodiment of the invention, the agent is a peptide such as a peptide containing a β₁ integrin-binding domain, specifically one comprising GRGDSP. The agent can also be a peptidomimetic compound.

[0034] In another embodiment of the invention, the agent is an antibody or a fragment thereof that specifically binds to the β₁ integrin cell surface receptor of leukocyte cells.

[0035] The present invention also provides a method of preventing a chronic infection from occurring due to the presence of bacterial cells on a surface of a foreign body in a subject, which comprises coating the foreign body before placing it in the subject with a fibrinolytic agent capable of preventing the accumulation of fibrin on the surface of the foreign body so as to permit leukocyte cells to reach and kill any bacterial cells present on the surface of the foreign body and thereby prevent the chronic infection.

[0036] In one embodiment of the invention, the foreign body is a prosthetic device, a catheter, or a suture.

[0037] In another embodiment of the invention, the subject is a mammal such as a human.

[0038] In yet another embodiment of the invention, the fibrinolytic agent is plasminogen activator such as urokinase, streptokinase, or tissue plasminogen activator.

[0039] The present invention further provides a method of treating a malignant tumor comprising of malignant tumor cells over and around which tenascin has been deposited, the malignant tumor being present in a subject, which comprises administering to the subject an agent capable of inhibiting signalling mediated by a β₁ integrin cell surface receptor of leukocyte cells in an amount effective to enhance the migration of leukocyte cells through the tenascin so as to permit the leukocyte cells to reach and kill the malignant tumor cells and thereby treat the malignant tumor.

[0040] In one embodiment of the invention, the subject is a mammal such as human.

[0041] In another embodiment of the invention, the leukocyte cells are polymorphonuclear leukocyte cells such as neutrophils, basophils, and eosinophils.

[0042] In yet another embodiment of the invention, the leukocyte cells are monocytes or macrophages.

[0043] In another embodiment of the invention, the leukocyte cells are lymphocyte cells such as NK cells and killer cells.

[0044] In yet another embodiment of the invention, the agent is a peptide such as a peptide containing a β₁ integrin-binding domain, specifically one comprising GRGDSP. The agent can also be a peptidomimetic compound.

[0045] In another embodiment of the invention, the agent is an antibody or a fragment thereof that specifically binds to the β₁ integrin cell surface receptor of leukocyte cells.

[0046] The present invention also provides a method of treating a chronic inflammation in a subject caused by an increase in the number of leukocyte cells present at the site of the chronic inflammation which comprises administering to the subject an agent capable of stimulating signalling mediated by a β₁ integrin cell surface receptor of leukocyte cells in an amount effective to inhibit the migration of leukocyte cells toward the site of the chronic inflammation so as to reduce the number of leukocyte cells present at the site and thereby treat the chronic inflammation.

[0047] In one embodiment of the invention, the subject is a mammal such as human.

[0048] In another embodiment of the invention, the leukocyte cells are polymorphonuclear leukocyte cells such as neutrophils, basophils, and eosinophils.

[0049] In yet another embodiment of the invention, the leukocyte cells are monocytes or macrophages.

[0050] In yet another embodiment of the invention, the agent is a peptide such as a peptide containing a β₁ integrin-binding domain, specifically one comprising GRGDSP. The agent can also be a peptidomimetic compound.

[0051] This invention will be better understood from the Experimental Details which follow. However, one skilled in the art will readily appreciate that the specific methods and results discussed are merely illustrative of the invention as described more fully in the claims which follow thereafter.

EXPERIMENTAL DETAILS

Example 1

[0052] The evolution of many chemically distinct chemoattractants and receptors suggests that in addition to promoting adhesion and directing PMN locomotion these molecules might regulate the strength of PMN adhesion to specific matrix proteins. The findings that TNF stimulates PMNs to adhere to fibrinogen-coated surfaces via CD11c/CD18 (7, 8), while phorbol dibutyrate stimulates PMNs to adhere to these surfaces via CD11b/CD18 (8, 9), prompted the examination of the effects of different chemoattractants on PMN migration through three dimensional matrices composed of fibrin, collagen IV or Matrigel, and through gels formed by thrombin treatment of cell-free plasma.

EXPERIMENTAL PROCEDURES

Reagents

[0053] Human monocyte recombinant IL-8 (Ser-IL-8)₇₂ and TNF-α were from Upstate Biotechnology Incorporated (Lake Placid, N.Y.). LTB4, fMLP and Ficoll-Hypaque were from Sigma (St. Louis, Mo.). Rhodamine conjugated polyethylene glycol was prepared as described (10).

Preparation of Boyden-Type Chemotaxis Chambers

[0054] Becton-Dickinson cell culture inserts (pore sizes 3 or 8 μm: Franklin Lakes, N.J.) were overlaid with the following proteins:

[0055] Fibrin gels: 1 Unit of thrombin (a gift from Dr. John Fenton, Albany Medical College, Albany, N.Y.), in 5 μl of PBS was added first to each insert. 0.1 ml phosphate buffered saline supplemented with Ca²⁺ and Mg²⁺ (PBS) containing 100 μg commercial grade fibrinogen (Calbiochem. Inc., San Diego, Calif.) or purified fibrinogen [a gift from Dr. Jeffery Weitz, (MacMaster University, Hamilton, On.)] was then placed into each 8.2 mm diameter insert on top of the thrombin. The mixture was incubated at 37° C. for 5 min to allow fibrin gel formation (determined by visual inspection). 1 Unit PPACK (Calbiochem Inc., San Diego, Calif.; 10⁻⁵ M final concentration), in 100 μl medium was added to each insert to inhibit thrombin, and gels were washed with 250 μl PBS to remove inactivated thrombin. The fibrin gels formed were about 1 mm thick as measured under a dissecting microscope.

[0056] Collagen type IV and Matrigel matrices: 0.1 ml PBS containing 100 μg human placental collagen IV (Fluka Chemical Corp., Ronkonkoma, N.Y.), or 80 μg of reconstituted basement membrane proteins (Matrigel, Collaborative Research, Bedford, Mass.), was placed into each insert and allowed to gel at room temperature for 24 hrs.

[0057] Clotted Plasma: Whole blood was collected and the cellular components were removed by centrifugation. The resulting plasma was mixed with an equal volume of PBS, and 100 μl of this mixture was placed into each insert containing thrombin and allowed to clot as described above. One unit of PPACK in 100 μl PBS then was added and the inserts were washed with 250 μl of PBS.

[0058] Fibrinogen or fibronectin: 0.1 ml of PBS containing 100 μg/ml fibrinogen or fibronectin (New York Blood Center, New York, N.Y.), was placed into each insert (pore size 3 μm). Inserts were incubated at 37° C. for 60 min and washed with 250 μl of PBS. Filters coated with fibrinogen or fibronectin were diffusely fluorescent as visualized by epifluorescent microscopy when incubated with the corresponding antibody [fluorescein-labeled anti-fibrinogen, or anti-fibronectin monoclonal antibodies (Cappel, Malvern, Pa.)], while uncoated filters, or filters incubated with fluorescein-labeled antibody of the opposite specificity, were not.

PMN Migration

[0059] PMNs were prepared from fresh heparinized blood from healthy adult volunteers by sedimentation on Ficoll-Hypaque gradients. Contaminating red blood cells were removed by hypotonic lysis, as described (7). The purity of PMN isolated by this method is >95% as determined by Wright-Giemsa staining (7). 10⁶ PMNs in 250 μl of PBS supplemented with 5.5 mM glucose and 0.1% human serum albumin (PBSG-HSA), were placed in the upper compartment of each insert and incubated for 0-6 hrs at 37° C. in a humidified atmosphere containing 95% air/5% CO₂. At the times and concentrations specified, chemoattractants/cytokines were added to the top or bottom compartment in 250 μl of PBSG-HSA. At the end of the incubation, the chambers were shaken to dislodge PMNs from the lower surface of the inserts. The medium in each lower compartment was collected and its content of PMNs was determined using either a Coulter Counter or a hemocytometer. Both methods gave similar results. Counts are expressed as the average number of PMNs that migrated into the lower compartment. Unless otherwise indicated, all values reported are the average of six data points from at least 3 independent experiments.

Confocal Microscopy

[0060] PMNs were suspended in medium containing 10 μM calcein/acetoxymethyl ester (Molecular Probes, Eugene, Oreg.), 0.02% (w/v) pluronic F-127 (Molecular Probes, Eugene, Oreg.), 2% heat inactivated calf serum (HyClone, Logan, Utah), and 0.2% DMSO, and mixed gently for 40 min at room temperature. Cells loaded with dye under these conditions exhibited no changes in motility (Mandeville and Maxfield, unpublished observations). The calcein-loaded cells were rinsed in PBSG-HSA and added to inserts containing fibrin gels in the presence or absence of TNF, fMLP, LTB4 or IL-8. Following incubation with PMNs, fibrin-coated filters were gently cut from their inserts using a razor blade, transferred to a glass slide, immersed in PBSG-HSA and covered with a glass coverslip. Migration of calcein-loaded PMNs through fibrin was analyzed using a Dialux 20× microscope (Leitz) fitted with a K2 Bio confocal scanning optical attachment using a Nipkow spinning disk. The microscope was equipped with an image intensifier, charge coupled device camera and video frame averager. The surface of the fibrin gel was identified using reflection interference contrast microscopy. Cells were imaged with a Plan-neofluor 25× fluorescence objective (NA=0.8) using fluorescein optics (490 nm excitation, 525 emission) and a spinning disk with pinhole apertures. Serial confocal optical sections were acquired at 1 μm intervals, digitized using the VolCon program (a PC-based image processing package, Indec Systems, Capitola, Calif.,). Three dimensional images were volume rendered using Microvoxel software (Index Systems), after passing data through a 3×3×3 Gaussian convolution filter. Each experiment was repeated at least twice using duplicate samples.

PMN Adhesion to Fibrin-Coated Surfaces

[0061] Fibrin coated Terasaki tissue culture plates were prepared as described (10). 5 μl of PBSG-HSA, containing PMNs (10⁶/ml) and the indicated chemoattractant, was added to each well of the plate. Plates were incubated at 4° for 30 min to allow PMNs to settle to the bottom of the wells and warmed to 37° for 15 min to allow PMNs to adhere. Non-adherent cells were removed as described (7), and 2.5% glutaraldehyde in PBS added to fix the adherent PMNs. PMNs adherent to each well were enumerated using a phase-contrast microscope. Values reported are the mean number of PMNs adherent to six wells from a representative experiment (n=3).

Exclusion of Rhodamine-Labeled Polyethylene Glycol from Zones of Adhesion of PMNs to Protein-Coated Surfaces

[0062] 10 kDa rhodamine labeled polyethylene glycol (Rh-PEG), prepared and used as described previously (10), does not bind to untreated glass, tissue culture plastic, or to cell membranes. Rh-PEG binds avidly to protein-coated surfaces, and can be detected easily by its fluorescence. Individual wells on glass microslides (Carlson Scientific, Peotone, Ill.) were coated with either fibrin, Matrigel or collagen IV in a manner similar to that for coating cell culture inserts except that 20 μl of the various solutions were used per well. 20 μl of PMNs (10⁶ cells/ml in PBSG-HSA) were added to each well and PMNs were allowed to adhere for 15 mins at 37°. The cells were washed in PBS, fixed with 3.7% paraformaldehyde in PBS for 10 min, washed again with PBS, and further incubated with 10 kDa Rh-PEG at room temperature for 60 min. The preparation then was washed with PBS and immediately observed by phase and fluorescent microscopy at 400× magnification. Average values from three different experiments are reported as the percentage of PMNs that excluded Rh-PEG from zones of adherence between the cells and the underlying matrix.

Degradation of ¹²⁵I-Labeled Fibrin Gels

[0063] 1.0 ml PBS containing 1 mg human fibrinogen, 1 mCi of Na¹²⁵I (NEN, Boston, Mass.), and 1 Iodobead (Pierce, Rockford, Ill.) was incubated for 15 mins on ice. ¹²⁵I-fibrinogen was separated from ¹²⁵I by gel filtration over a Speedy Desalting Column (Pierce). >97% of the ¹²⁵I recovered in the fibrinogen-containing fractions was precipitable with 20% trichloracetic acid. 5 μl PBS containing 1 Unit of thrombin, followed by 0.1 ml PBS containing 10⁶ cpm of ¹²⁵I-fibrinogen (˜10 μg) and 100 μg unlabeled fibrinogen were added to each insert, as described above. The resulting ¹²⁵I-labeled fibrin gels were treated with PPACK, washed, and incubated with 10⁶ PMNs as described in the text. At various times after PMN addition the medium was removed from the upper and lower compartments, and added to 0.1 ml of PBS containing 10 mg/ml bovine serum albumin (BSA). Ice-cold trichloracetic acid was added to a final concentration of 20% and samples were centrifuged to sediment acid insoluble materials. TCA soluble and insoluble materials were separated by centrifugation and ¹²⁵I in each fraction was determined using an LKB minigamma counter.

Results

IL-8 and LTB4, but Not TNF or fMLP, Promote the Migration of PMNs through Fibrin Gels

[0064] PMNs were placed into the upper compartment of inserts containing fibrin gels. IL-8, LTB4, fMLP, or TNF was placed in the medium in the lower compartment and the chambers were incubated at 37° C. for 6 hrs. IL-8 or LTB4 stimulated 12-25% of PMNs to migrate through the fibrin gels and into the lower compartment. In the absence of a chemoattractant or in response to various concentrations of TNF (10⁻⁹-5×10⁻⁶ M) or fMLP (10⁻¹⁰-10⁻⁶ M), fewer than 0.3% of the PMNs migrated through fibrin gels into the lower compartments (FIGS. 1A and 2). Moreover, PMNs did not migrate through fibrin in response to the addition of 2-10% zymosan-activated human plasma (C5a) in the lower compartment.

[0065] PMNs stimulated by IL-8 or LTB4, but not by TNF or fMLP, migrated through fibrin gels formed by thrombin treatment of commercial-grade fibrinogen (FIG. 1A) or of purified fibrinogen, or through plasma gels formed by thrombin treatment of human plasma (FIG. 1B). Moreover, the presence of 20% human serum in the medium in both upper and lower compartments did not alter PMN migration through fibrin gels in response to IL-8, nor did the presence of serum promote PMN migration through fibrin gels in response to TNF or fMLP. That PMNs migrate through fibrin gels in the presence of human serum, and through gels formed from whole human plasma, indicates that IL-8 promotes PMN migration through fibrin gels containing the complex mixture of plasma proteins found under physiological conditions.

[0066] The percent of PMNs that migrated through fibrin gels varied with the concentration of IL-8 or LTB4 placed in the bottom compartment (FIG. 2B). Maximal PMN migration occurred with 0.7×10⁻⁷ M IL-8 or 0.2×10⁻⁷ M LTB4 (FIG. 2B). PMN migration decreased dramatically when IL-8 was used at concentrations >10⁻⁷ M, consistent with the report of Smith et. al. (11) that high concentrations of IL-8 desensitize PMNs. In contrast, there was no indication of PMN desensitization in response to supra-optimal concentrations of LTB4 (FIG. 2B).

[0067] To determine whether IL-8 and LTB4 promote PMN migration through fibrin gels by stimulating chemotaxis or chemokinesis we performed a checkerboard-type analysis (12). Few PMNs migrated through fibrin gels when IL-8 or LTB4 was placed in the upper compartment, or when the upper and lower compartments contained equal concentrations of IL-8 or LTB4 (FIGS. 1A and 1B). As the difference in IL-8 or LTB4 concentrations between the upper and lower compartments decreased, the number of PMNs that migrated through the fibrin gels also decreased (FIGS. 3A and 3B). These results indicate that PMN migration through fibrin gels in response to IL-8 or LTB4 reflects chemotaxis, not chemokinesis.

[0068] Between 25-50% more PMNs migrated through fibrin in response to LTB4 than to IL-8. It is unlikely that this difference reflects the response of different PMN subpopulations to LTB4 vs IL-8 since the same percentage of PMNs traversed fibrin gels in response to optimal concentrations of both LTB4 and IL-8 in the lower compartment as to LTB4 alone. Other investigators have reported that only 20-50% of PMNs migrate through filters (13), natural matrices, and cellular barriers (14), when stimulated by these chemoattractants. Since virtually all PMNs orient and crawl on surfaces when exposed to the chemoattractants (3), it is evident that all PMNs responded to them. The reason(s) why only a fraction of PMNs migrate through artificial or natural barriers in response to chemoattractants is unknown.

[0069] PMNs migrated through fibrin gels more rapidly in response to an optimal concentration of LTB4 than to an optimal concentration of IL-8 (FIG. 4). Ten percent of LTB4-stimulated PMNs migrated through fibrin gels within 2 hrs while fewer than 0.5% of IL-8-stimulated PMNs migrated through these gels in this time period (FIG. 4). By 6 hrs, maximal numbers of PMNs had migrated through fibrin gels in response to either IL-8 or LTB4.

[0070] To visualize the interactions of chemoattractant-stimulated PMNs with fibrin gels, PMNs prelabeled with calcein (15), were added to the upper compartment of inserts containing fibrin gels. Chemoattractants were added to the medium in the lower compartment, the chambers were incubated at 37° C., and at the times indicated the fibrin-coated filters were removed and examined by confocal microscopy. After a 1 or 4 hr incubation with fMLP or TNF, almost all the cells remained on the gel's surface; fewer than 5% of TNF- or fMLP-stimulated PMNs penetrated a short distance into the fibrin gels; (FIGS. 5A, 5B, 5C, 5D, 5E, and 5F). In contrast, greater than 80% of IL-8-stimulated PMNs migrated deeply into the fibrin gels after a 4 hr incubation (FIGS. 5A, 5B, 5C, 5D, 5E, and 5F). Greater than 80% of LTB4-stimulated PMNs began to migrate into the fibrin gel after 1 hr, while few IL-8 stimulated PMNs penetrated the fibrin at this time. These results show that TNF and fMLP do not promote PMN invasion of fibrin, and that LTB4 stimulates PMNs to enter fibrin gels more rapidly than IL-8. The latter finding is consistent with the more rapid transit of fibrin gels by LTB4- than IL-8-stimulated PMNs described in FIG. 4.

[0071] To further examine whether proteolysis of fibrin accounted for the selective ability of IL-8- or LTB4-stimulated PMNs to traverse these gels, the release of ¹²⁵I-labeled products was measured from ¹²⁵I-fibrin incubated with PMNs for 6 hrs at 37° C. in the presence or absence of each of these chemoattractants. The rare and extent of release of ¹²⁵I-labeled acid soluble and acid precipitable products was similar for all four chemoattractants (FIG. 6). Even in the presence of 20% serum, chemoattractant-stimulated PMNs released no more ¹²⁵I-labeled products than unstimulated PMNs. These results suggest that fibrin degradation does not account for the selective ability of LTB4- and IL-8-stimulated PMNs to traverse fibrin gels.

LTB4, IL-8, TNF and fMLP Promote PMN Migration through Gels Formed of Matrigel and Collagen IV

[0072] To confirm that the inability of TNF-, fMLP-, or zymosan-activated human plasma-stimulated PMNs to migrate through fibrin gels reflected an effect of the interaction between the fibrin matrix and chemoattractant-stimulated PMNs, and not a general effect of any three dimensional matrix on PMNs stimulated with these chemoattractants, the ability of TNF, zymosan activated human plasma and fMLP to promote PMN migration through gels composed of basement membrane proteins (Matrigel) or collagen IV was examined (FIGS. 7A and 7B). TNF, fMLP, IL-8, zymosan-activated human plasma, or LTB4 added to the bottom chamber stimulated PMN migration through these gels (FIG. 7A). To determine whether fibrin affected PMN migration through collagen matrices, inserts coated with collagen IV gels were incubated with fibrinogen and thrombin to form fibrin sandwich on top of the collagen gels, and washed with PPACK-containing buffer. PMNs were added to the upper compartment and TNF to the lower compartment. The presence of fibrin prevented PMN migration through the collagen gels in response to TNF by about 75% (FIG. 7A). These results confirm that the effect of fibrin is selective and that it affects PMN migration in response to a specific subset of chemoattractants.

[0073] To determine whether protein monolayers had the same effects on PMN migration as gels, inserts were coated with fibrinogen or fibronectin. The adsorption of these proteins to the filters that form the floor of the inserts was confirmed by immunofluorescence microscopy, as described in Experimental Procedures. fMLP, TNF, IL-8 and LTB4 all promoted PMN migration through filters to which fibrinogen or fibronectin had been adsorbed (FIG. 7B).

PMNs Adhere More Closely to Fibrin in Response to fMLP or TNF than to LTB4 or IL-8

[0074] Is there a relationship between the ability of a chemoattractant to stimulate PMN migration through fibrin and its ability to promote close apposition of PMNs to fibrin? PMNs were incubated on fibrin-coated surfaces in the presence or absence of a chemoattractant for 15 min at 37° C. As expected, TNF, fMLP, LTB4 and IL-8 were equally effective in stimulating PMN adherence to fibrin (>200 chemoattractant-stimulated PMNs vs ˜10 unstimulated PMNs adhered per mm²). The closeness of PMN adhesion to fibrin was evaluated by the ability of 10 kDa Rh-PEG (8, 10), to penetrate into the zones of adhesion between chemoattractant-stimulated PMNs and fibrin. By this measure 70-80% of adherent TNF- or fMLP-stimulated PMNs excluded Rh-PEG from their zones of contact with the fibrin (FIG. 8). In contrast, only about 15% of adherent LTB4- or IL-8-stimulated PMNs formed adhesive zones that excluded Rh-PEG (FIG. 8). Furthermore, the adhesive zones formed by this 15% of IL-8-stimulated PMNs were at least 50% smaller in area than those formed by TNF- or fMLP-stimulated PMNs as judged by the area from which Rh-PEG was excluded.

[0075] Previous studies (10) showed that the exclusion of fluorescein-conjugated F(ab)₂ anti-fibrinogen from zones of contact between ADP-stimulated platelets and fibrinogen-coated surfaces is a useful measure of the closeness of apposition between platelet membranes and the substrate. Therefore, the exclusion of fluorescein-conjugated F(ab)₂ anti-fibrin from zones of contact between LTB4- or IL-8-stimulated PMNs and fibrin was used as a measure of the interaction of these cells with fibrin-coated surfaces. About 50% of fibrin-adherent LTB4- or IL-8-stimulated PMNs formed adhesive zones that excluded this high molecular weight (100 kDa.) probe. As expected from studies with Rh-PEG (FIG. 8), >99% of fibrin-adherent TNF- or fMLP-stimulated PMNs excluded fluorescein-conjugated F(ab)₂ anti-fibrin from their zones of contact with fibrin (data not shown). Thus, LTB4- or IL-8-stimulated PMNs adhere more closely to fibrin than unstimulated PMNs, even though these chemoattractants do not promote the very close apposition characteristic of fMLP- or TNF-stimulated PMNs.

The Effect of Combinations of Chemoattractants on Migration of PMNs through Fibrin Gels

[0076] The inability of fMLP- or TNF-stimulated PMNs to migrate through fibrin can be interpreted in at least two ways. First, fibrin blocks the capacity of PMNs to respond to fMLP or TNF. This seems unlikely since fMLP and TNF promote close apposition between PMNs and fibrin coated surfaces (FIG. 8). Second, fMLP or TNF signal PMNs to become sessile when they interact with fibrin. To examine the second possibility, the effects of combinations of chemoattractants on PMN migration through fibrin gels were monitored (FIGS. 9A and 9B). The presence of fMLP in the bottom compartment of the inserts reduced PMN migration through fibrin gels in response to IL-8 or LTB4 in a concentration dependent fashion. Higher concentrations of fMLP were required to effect equal inhibition of migration of LTB4-stimulated PMNs vs IL-8 stimulated PMNs (FIG. 9B). TNF had a small, reproducible, but statistically insignificant inhibitory effect on the migration of PMNs in response to IL-8 and no measurable effect on PMN migration in response to LTB4 (FIG. 9A). Thus, fMLP selectively reduced PMN migration through fibrin gels in response to IL-8 or LTB4 (FIG. 9B).

[0077] The effects of combinations of chemoattractants on formation of close apposition of adhesion of PMNs with fibrin were also examined. fMLP in combination with IL-8 or LTB4 induced about 50% of PMNs to form zones of adhesion that excluded 10 kDa. Rh-PEG (FIG. 8). In contrast, only 15% of PMNs stimulated with IL-8 or LTB4 alone formed close zones of adhesion (FIG. 8). Thus, the capacity of PMNs to form close zones of adhesion on fibrin was inversely associated with the capacity of PMNs to migrate through fibrin gels under conditions where PMNs were stimulated with TNF, fMLP, IL-8 or LTB4 given alone or with fMLP in combination with IL-8 or LTB4.

[0078] To determine the machanism by which fibrin blocks PMN migration in response to fMLP, the effects of anti-integrin antibodies were tested (FIGS. 10A and 10B). PMNs incubated with anti-β₁ integrin antibodies (2 μg/ml) or the peptide GRGDSP (SEQUENCE ID NO. 1) (1 mg/ml), but not GRGESP (SEQUENCE ID NO. 2), migrated through fibrin gels in response to fMLP. Control experiments showed that anti-β₁ antibodies did not affect LTB4-stimulated PMN migration through fibrin. These studies show that interactions between PMN β₁ integrins and matrix-associated ligands regulate PMN migration. They suggest that fMLP, but not LTB4 signals binding of β₁ integrins to β₁ ligands (e.g. RDG) on fibrin. These studies also suggest that ligation of β₁ integrins signals fMLP-stimulated PMN to become sessile, and that by blocking β₁ integrins with antibodies or peptides, PMNs are able to migrate into tissue sites containing fibrin, from which PMN would otherwise be excluded.

Discussion

Matrix Proteins Modulate Cellular Responses to Hormones, Cytokines, and Growth Factors

[0079] Matrix proteins exert profound effects on adhesion, differentiation, migration, and/or secretion of epithelial cells (16, 17), endothelial cells (18), neurons (19, 20) and leukocytes (7, 9, 21-27). Matrix proteins also affect the ability of many types of cells to respond to hormones, growth factors, and cytokines (28, 29). The findings that some chemoattractants (e.g., fMLP, TNF, C5a), promote PMN migration in the context of two types of extracellular matrix proteins (e.g., matrigel and collagens IV) (FIGS. 5A, 5B, 5C, 5D, 5E, 5F, 7a, and 7B), and PMN immobilization in the context of another (e.g., fibrin) (FIGS. 1A, 1B, 2A, 5A, 5B, 5C, 5D, 5E, and 5F), are the first to show that specific matrix proteins regulate leukocyte chemotaxis. They show that fibrin gels, fibrin-impregnated collagen gels, and fibrin-containing plasma clots present selective barriers to the migration of fMLP- or TNF-stimulated PMNs and that chemotaxis of PMNs through three dimensional matrices is regulated by both the specific chemoattractant and the protein composition of the matrix with which the cells are in contact.

Matrix Proteins Regulate PMN Adhesion, Phagocytosis and Secretion

[0080] Previous studies (7, 9, 21) have shown that TNF or phorbol ester stimulated PMNs adhere to fibrinogen-coated surfaces via different beta-2 integrins (CD11b/CD18 vs CD11c/CD18, respectively) and Lundgren-Akerlund et al. (22), and Thompson and Matsushima (23), have reported that fMLP stimulated PMNs adhere to protein coated surfaces with different efficiencies depending on the matrix protein used to coat these surfaces. With respect to phagocytosis, Pommier et al. (24), and Wright et al., (25) showed that the interaction of fibronectin with its β₁ integrin activates complement receptors (CD11b/CD18) on monocytes and PMNs to phagocytose C3bi-coated particles. With respect to secretion, Monboisse et al., (26, 27) reported that the interaction of unstimulated or chemoattractant- stimulated PMNs with collagen I-coated surfaces induces the secretion of proteolytic enzymes and O₂⁻. In contrast, preincubation of PMNs with collagen IV blocks the ability of collagen I and of fMLP to stimulate resting PMNs to secrete these products (26, 27). Similarly, adhesion of TNF-stimulated PMNs to extracellular matrix proteins that express Arg-Gly-Asp motifs enhances PMN secretion (30). The findings reported here add chemotaxis to the list of leukocyte functions modulated by their contact with matrix proteins.

Relationship Between Strength of Adhesion, Closeness of PMN Apposition to the Substrate, and PMN Migration

[0081] DiMilla at al (31), have explored the relationship between strength of cell adhesion to a substrate and cell migration by following the spontaneous migration of human smooth muscle cells on surfaces that had absorbed varying concentrations of fibronectin or collagen IV. Under the conditions of their experiments, the rate of cell migration was maximal at an intermediate level of cell-substratum adhesiveness. Goodman et al. (32), found a similar biphasic relationship between the movement of murine skeletal myoblasts and the absorbed concentration of laminin on the substrate.

[0082] While the strength of PMN adhesion to fibrin was not measured directly, the “closeness” of apposition between PMNs' matrix-adherent surfaces and matrices containing different proteins was examined by measuring the permeability of zones of contact between PMNs and the underlying matrix to macromolecular probes. “Close” apposition is defined as the exclusion of 10 kDa Rh-PEG from zones of contact between the PMNs' substrate-adherent membranes and the matrix, and “loose” apposition as permeation of 10 kDa Rh-PEG into these zones. These results show that chemoattractants, such as IL-8 and LTB4, elicit “loose” apposition between PMNs and fibrin gels and promote PMN migration through these gels. Chemoattractants, such as fMLP and TNF, that signal “close” apposition between PMNs and fibrin gels do not promote PMN migration through these gels. This correlation was further supported by the findings that PMNs stimulated by any of these chemoattractants formed loose zones of adhesion (e.g., permeable to 10 kDa Rh-PEG) on collagen IV or Matrigel (FIG. 8), and migrated through these matrices (FIG. 7A); and that fMLP induced LTB4 or IL-8 stimulated PMNs to form close zones of apposition to fibrin and cease migration (FIGS. 8, 9A and 9B). Thus, there is an inverse association between close PMN interaction with a matrix protein and the ability of PMNs to migrate though gels containing it. These findings suggest that “close” and “loose” apposition between PMNs and matrix proteins as defined here, are functionally equivalent to very strong and intermediate adhesion between cells and matrix, respectively, as defined by DiMilla et al (31).

Fibrin Degradation is Not Required for PMN Chemotaxis

[0083] The zones of close apposition formed between fMLP- or TNF-stimulated PMNs and fibrin gels are impermeant to molecules of >10 kDa thereby excluding virtually all plasma protease inhibitors such as alpha₁ anti-plasmin and alpha₂ macroglobulin. Therefore, leukocyte proteases secreted into these zones function virtually uninhibited (33). In contrast, IL-8- or LTB4-stimulated PMNs adhere more loosely to fibrin-gels. Under these conditions, plasma protease inhibitors should have ready access to zones of contact with the substrate and inhibit the action of leukocyte proteases. Thus, fMLP- or TNF-stimulated PMNs might be expected to digest fibrin gels more efficiently than IL-8- or LTB4-stimulated PMNs. This was not observed (FIG. 6). There were no significant differences in the amount of radiolabel released from ¹²⁵I-labeled fibrin by migrating LTB4- or IL-8-stimulated PMNs vs sessile fMLP- or TNF-stimulated PMNs, even in the presence of 20% serum. These findings suggest that PMNs that migrate through fibrin gels in response to IL-8 and LTB4 do so by mechanisms other than proteolyzing these gels. Lanir et al., (34) came to a similar conclusion in their studies of guinea pig macrophage migration through fibrin gels.

[0084] That fMLP and TNF promote PMN migration through fibrinogen-coated filters (FIGS. 7A and 7B), is probably related to the observations that fMLP-stimulated PMNs efficiently degrade substrate-adherent proteins including fibrinogen (33), and fibronectin (35), thereby removing these proteins from the substrate and facilitating PMN movement.

How Do Matrix Proteins Regulate Leukocyte Chemotaxis?

[0085] The results shown in Example 1 indicate the following: Different chemoattractants activate different subsets of PMN integrins to bind to ligands on matrix proteins (7-9). The interaction of each type of activated PMN integrin with its cognate ligand on a matrix protein specifies a distinct set of cellular migratory or sessile responses. These responses may result from direct interaction of a matrix protein with the activated integrin or by signals sent by the activated integrin to other integrins on the same cell. There are several instances where ligation of one type of integrin by matrix proteins modulates the activity of another type of integrin. As described above, Pommier et al., (24) and Wright et al. (25) showed that ligation of β₁ integrins by fibronectin activates the β₂ integrin CD11b/CD18, (complement receptor 3) on monocytes and PMNs to phagocytose C3bi-coated particles. It was previously shown that ligation of α₅β₁ on platelets by fibronectin stimulates platelets to form close zones of apposition with fibrinogen (10). Hutalia et al, (36) reported that ligation of α₅β₂ integrin by RGD peptides induces the expression of matrix metalloproteinases by fibroblasts, whereas ligation α₄β₁ integrin by intact fibronectin suppresses matrix metalloproteinase expression.

[0086] In vivo inflammatory stimuli elicit the generation of multiple chemoattractants/cytokines. The present findings show that a hierarchy of cellular responses is generated when different combinations of chemoattractant receptors are stimulated simultaneously. Signals generated by fMLP receptors appear to override signals produced by LTB4 or IL-8 receptors, thereby blocking the ability of LTB4 or IL-8 to stimulate PMN migration through fibrin gels (FIG. 8). In contrast, signals generated by TNF receptors have no effect on LTB4-stimulated PMN migration through fibrin gels, and a very weak inhibitory effect on IL-8-stimulated PMN migration through these gels (FIG. 8).

[0087] PMN chemotaxis through three dimensional lattices composed of extracellular matrix proteins is regulated both by signals initiated by a specific chemoattractant, and by signals generated when specific PMN receptors interact with their cognate ligands on extracellular matrix proteins. Viewed from this perspective each of the many different chemoattractants provides PMNs both with general instructions to crawl, and with specific instructions to become sessile when specific receptors on these cells contact their cognate ligands on matrix proteins. Thus, chemoattractants provide tissue localization instructions for PMNs. It seems likely that chemoattractants also provide such instructions to other types of leukocytes as well.

[0088] PMNs stimulated with zymosan-activated human plasma (C5a) did not migrate across fibrin-coated inserts but did migrate across matrigel-coated inserts. Thus, C5a, like fMLP and TNF, signals PMNs to stop migrating when they contact fibrin.

Example 2

[0089] The inhibitory effects of extracellular matrix proteins on chemotaxis of leukocytes (7, 8, 9, 65) prompted the examination the effects of tenascin on these processes. The present findings show that tenascin blocks chemotaxis of polymorphonuclear and mononuclear phagocytes across reconstituted basement membrane (Matrigel)-coated filters in a β₁ integrin-dependent process.

Experimental Procedures

Cells

[0090] Polymorphonuclear leukocytes (PMN), were prepared as described (7) from heparinized human blood by sedimentation on Ficoll-Hypaque gradients. Contaminating red blood cells were removed by hypotonic lysis. The purity of PMN isolated by this method was >95% as determined by Wright-Giemsa staining.

[0091] Mononuclear cells were isolated by centrifugation of heparinized human blood on Ficoll-Hypaque gradients as described (65, 66). The mononuclear cell fraction was resuspended in RMPI 1640 medium supplemented with 10% pooled human serum or autologous serum and used immediately for monocyte migration studies. For some experiments, monocytes were obtained by centrifugation of whole blood or of white blood cells concentrated from a unit of blood (leukopak), on Nycodenz gradients as described (39). More than 90% of the nucleated cells obtained by this Nycodenz method were monocytes, as assessed by their ability to phagocytose IgG-coated red blood cells.

[0092] Cultured monocytes were prepared by allowing 10⁷ total mononuclear cells, suspended in 10 ml of RMPI 1640 medium supplemented with 10% pooled human serum (1640+HS), or 10% autologous serum (1640+AS), to adhere to Falcon T-150 tissue culture Petri dishes for 2 h at 37° C. Non-adherent cells were removed by washing, leaving an adherent cell population consisting of greater than 98% monocytes as measured by their capacity to phagocytose IgG coated sheep red blood cells. For migration studies, monocytes were maintained in culture for 24 h in RPMI 1640+HS or AS, and detached from the dishes by gentle pipetting of 10 ml of ice cold phosphate buffered saline (without Ca²⁺ or Mg²⁺) containing 1.0 mM EDTA. The cells recovered were resuspended in RPMI-1640+HS as described (65).

Protein-Coated Filters

[0093] Cell culture inserts containing polyethylene terephthalate filters, 8-μm pore size (Becton-Dickinson), were overlaid with 0.1 ml of Matrigel (20-25 μg protein/filter) (Collaborative Research, Bedford, Mass.), and incubated at room temperature until they dried. These Matrigel-coated filters were washed with phosphate buffered saline containing 1.0 mM Mg²⁺ and 1.0 mM Ca²⁺ (PBS). 0.1 ml of a PBS solution (pH 7.2) containing the indicated amount of purified chick brain tenascin was added to some of the inserts. The filters were incubated at room temperature until they dried. These protein-coated filters were washed again with PBS and used within 12 h for cell migration studies. To prepare collagen I-coated inserts, filters were coated with rat tail collagen I (ICN Biochemicals, Costa, Mesa, Calif.) (400 μg/ml in PBS), by adding 0.1 ml of this solution to an insert and incubating the inserts at room temperature for 24 h. Some of these collagen I-coated filters were then incubated with tenascin as described above.

Cell Migration

[0094] Monocytes: Cell culture inserts were placed in 16 mm wells containing 0.5 mls of RPMI-1640+HS or AS in the presence or absence of a chemoattractant. 0.5 ml of RPMI-1640+HS or AS serum containing between 2-10×10⁵ mononuclear phagocytes was added to the upper chamber of the inserts and the inserts were placed in a humidified CO₂ incubator at 37° C. After 24 h the medium in the lower chamber was recovered and its cell content assayed using either a Coulter counter or a hemocytometer. No significant increase was observed in the number of monocytes that migrated into the lower compartment at times greater than 24 h. Cell counts reported are the average number of cells recovered from the medium in the lower compartment of chemotaxis chambers. Over 90% of the cells in the lower chamber were identified as monocytes based on their morphology, their capacity to phagocytose IgG coated sheep red cells, and their staining with fluorescein-conjugated anti α,β monoclonal antibody (Oncogene Sciences, Uniondale, N.Y.). Unless otherwise indicated, all values are the average of duplicate samples run in parallel in a representative experiment. Each experiment was repeated at least three times with similar results.

[0095] PMN: 250 μl of PBS [supplemented with 5.5 mM glucose and 0.1% human serum albumin (HSA) (PBSG-HSA)] containing 1×10⁶ PMNs was placed in the upper compartment of each insert. 250 μl of PBSG-HSA with or without chemoattractant, as indicated, was added to the bottom compartment. The inserts were incubated for about 4 h at 37° C. in a humidified atmosphere containing 95% air/5% CO₂. No further increase in the number of PMNs was observed in the lower compartment beyond 4 h. The medium in the lower compartment was collected and its content of PMN determined using a Coulter Counter, as described in Example 1.

Tenascin

[0096] To isolate tenascin, 14-day embryonic chick brains were homogenized in the presence of protease inhibitors and the extracts were clarified as previously described (61). Dry CsCl was added to a final concentration of 0.5 g/ml and the extract was centrifuged (18 h, 45,000 rpm, 20° C.) in a Beckman VAC 50 rotor. The resulting density gradients were fractionated into five 8-ml fractions. The third and fourth fractions a rich source of relatively pure tenascin, were pooled, dialyzed versus 10 mM Tris pH 8.0, then incubated with chondroitin ABC lyase (Seikagaka America), in the presence of protease inhibitors (61), to degrade contaminating proteoglycans. The sample then was lyophilized, resuspended in 4 M guanidine-HCl/0.1 M Tris (pH 7.6), and fractionated on a 1.5×100 cm column containing Sephacryl S-500 (Pharmacia, Piscataway, N.J.), equilibrated in the same buffer. Tenascin-rich fractions were pooled, dialyzed, lyophilized, resuspended in a small volume of guanidine buffer, and finally dialyzed extensively vs PBS. This procedure yielded large amounts of purified tenascin which migrated as characteristic 220, 200, and 190 kD polypeptides when analyzed by SDS-PAGE under reducing conditions (44). Human tenascin was obtained from GIBCO-BRL, (Grand Island, N.Y.). To remove the detergent in the preparation, the sample was run over a gel filtration column in the presence of 4 M guanidine-HCl; the tenascin containing fractions were then dialyzed extensively vs PBS.

Measurement of Tenascin Bound to Matrices

[0097] Chick tenascin was radiolabeled using chloramine T (67), and mixed with unlabeled tenascin at a 1:100 protein ratio. 250 μl of PBS containing varying amounts of this mixture was added to inserts coated with Matrigel or collagen I. The inserts were incubated at room temperature for 4 h at 37° C. in a humidified 95%air/5% CO₂ atmosphere and washed with PBS. The filters were cut from the inserts with a scalpel, and assayed for 125I in a Beckman gamma counter.

Reagents

[0098] Monoclonal antibody P4C10 (anti-β chain of human beta-1 integrin), was from GIBCO-BRL. Fluorescein conjugated monoclonal antibody against the β chain of human beta-2 integrins (anti-β₂-CP14F) was obtained from Oncogene Sciences (Uniondale, N.Y.). Fluorescein conjugated anti CD11b monoclonal antibody was from AMAC Inc (Westbrook, Me.). Monoclonal anti-CD11c/CD18 (LeuM5) was from Organon-Toknika Inc. (Malvern, Pa.). F(ab)′₂ fragments of anti-tenascin antibodies were prepared as described (46).

[0099] Chondroitin sulfate proteoglycan monomers were purified and antibodies prepared against these proteoglycan monomers as described (37). The F(ab)′₂ fragments used in the present study were prepared from total anti-proteoglycan IgG. These antibodies were not further purified by affinity chromatography and therefore recognize both 400 kD and 250 kD proteoglycan core proteins (67).

Results

Tenascin Blocks Chemotaxis of Monocytes and Neutrophils, through Matrigel-Coated Filters

[0100] About 20% of freshly isolated human monocytes, 15% of cultured monocytes and 10% of PMNs migrated through Matrigel-coated culture inserts in response to fMLP, LTB4, or TNF (FIGS. 11A, 11B, and 12). Monocytes began to appear in the lower compartment at 12 h, and reached maximum numbers by 16-24 h. PMNs began to appear in the lower compartment by 2 h, and reached a maximum by 4 h. Fewer than 2% of added monocytes or PMN, migrated into the lower compartment in the absence of a chemoattractant (FIGS. 11A, 11B, and 12).

[0101] Addition of chick brain tenascin to the Matrigel significantly reduced monocyte and PMN migration in response to TNF, fMLP or LTB4 (FIGS. 11A, 11B and 12). The presence of tenascin had no significant effect on the limited number of monocytes that migrated in the absence of chemoattractant (FIGS. 11A and 11B). In contrast, tenascin further reduced the small number of PMN that migrated across Matrigel in the absence of chemoattractant (FIG. 12). The extent to which tenascin inhibited chemoattractant-stimulated monocyte or PMN migration varied from 65-80% depending on the chemoattractant used (FIGS. 11A, 11B, and 12). The ability of tenascin obtained from cultured human glioma cells to effectively inhibit leukocyte migration was examined. Indeed, the addition of 5 μg of human tenascin to the Matrigel-coated filters reduced the number of monocytes or PMNs migrating in response to a chemoattractant by at least 50% (FIGS. 13A and 13B).

[0102] The effect of chick brain tenascin on TNF-stimulated migration of monocytes varied with the amount of tenascin added (FIG. 14). Addition of about 0.75 μg tenascin caused half maximal inhibition of TNF-stimulated monocyte migration (FIG. 14). To confirm that tenascin bound to the Matrigel, Matrigel-coated inserts were incubated with varying amounts of concentrations of ¹²⁵I-labeled chick tenascin for 4 h at 37° C. The inserts then were washed with PBS and the bound radioactivity was determined. Near plateau binding of radiolabeled tenascin was obtained with the addition of 0.625-1.25 μg of chick tenascin to the Matrigel coated filters (FIG. 15). This resulted in the adsorption of about 0.2 μg of tenascin per filter. Once bound, less than 1% of the ¹²⁵I-labeled tenascin eluted from the filters into either the upper or lower compartment of the chambers during a 4-6 h incubation at 37° C. Thus, ˜99% of tenascin remained bound to Matrigel-coated filter. The capacity of tenascin to inhibit monocyte migration (FIG. 14) was roughly proportional to the amount of tenascin that bound to the filter (FIG. 15), indicating that tenascin bound to the Matrigel matrix, not soluble tenascin, blocked monocyte and PMN migration.

Tenascin Blocks Migration of Monocytes through Collagen I Gels

[0103] The effects of tenascin on monocyte migration through another extracellular matrix, collagen I were examined. Twelve percent of TNF- and 18% of LTB4-stimulated monocytes migrated through cell culture inserts coated with collagen I (FIG. 16). Addition of chick brain tenascin to collagen I coated inserts reduced TNF- or LTB4-stimulated monocyte migration by at least 60% (FIG. 16). Binding studies with ¹²⁵I-labeled chick tenascin revealed that similar amounts of tenascin bound to collagen I-coated filters as to Matrigel-coated filters.

Effect of F(ab)′₂ Anti-Tenascin on the Migration of Monocytes Across Filters Coated with Matrigel and Tenascin

[0104] Monocytes or PMN were added to the upper compartment of inserts coated with Matrigel alone or with Matrigel and tenascin. F(ab)′₂ anti-tenascin (2 μg/ml) was added to the medium in the upper compartment and LTB4 (10⁻⁷ M) was added to the lower compartment. F(ab)′₂ fragments of anti-tenascin antibody had no significant effect on PMN migration across filters coated with Matrigel alone (FIG. 17A), but reduced monocyte migration across this matrix by about 40% (FIG. 17B). However, F(ab)′₂ fragments of anti-tenascin antibody restored PMN chemotaxis across filters coated with Matrigel and tenascin to about 75% of control values (FIG. 17B), and increased substantially monocyte migration across tenascin coated Matrigel (FIG. 17A).

[0105] Because of their affinity for tenascin, proteoglycans may contaminate some tenascin preparations (46). Therefore, the effects of F(ab)′₂ fragments of polyclonal anti-proteoglycan on monocyte migration across filters coated with tenascin and Matrigel were examined. F(ab)′₂ anti-proteoglycan (2-5 μg/ml) did not reverse tenascin's inhibitory effect on monocyte migration across filters coated with Matrigel and tenascin, and did not significantly affect monocyte chemotaxis across filters coated with Matrigel alone. These studies suggest that tenascin inhibits migration by interacting with monocytes and not by blocking some matrix component required for their migration.

Antibodies that Block β₁ Integrins Reverse the Inhibitory Effects of Tenascin on Monocyte and PMN Migration through Filters Coated with Matrigel and Tenascin

[0106] Endothelial cell attachment and spreading on human tenascin has been shown to be partially mediated by β₁ integrins (60). Similarly, Prieto et al. (53, 54), showed that anti-β₁ integrin antibodies block the adhesion of glioma and carcinoma cell lines to tenascin. Therefore, the effects of anti-β₁ antibodies on monocyte and PMN chemotaxis through filters coated with Matrigel alone or with Matrigel and tenascin were examined. Monocytes or PMNs were preincubated for 30 min at 4° C. in medium containing 2 μg/ml of the test antibody. The suspension then was added to the upper compartment of the inserts.

[0107] LTB4 was added to the lower compartment and the inserts were incubated at 37° C. for 24 h for monocytes or 4 h for PMN. A monoclonal antibody directed against β₁ integrins (P4C10) had no effect on monocyte chemotaxis through filters coated with Matrigel alone but reversed the inhibitory effect of tenascin on monocyte migration through Matrigel/tenascin coated filters by about 50% (FIGS. 17A and 17B). Control experiments showed that monoclonal antibody P4C10 also reversed tenascin's inhibitory effect on TNF-stimulated monocyte chemotaxis by about 60%. P4C10 reversed almost completely the inhibitory effect of tenascin on LTB4- (FIG. 17B) or TNF-stimulated chemotaxis of PMN across filters coated with Matrigel and tenascin.

[0108] To confirm that the effect of P4C10 was due to its interaction with β₁ integrins, the effects of other anti-integrin antibody, A₁₁B₁₁, on chemotaxis of monocytes through filters coated with Matrigel and tenascin were examined. A₁₁B₁₁ (2 μg/ml) blocked the inhibitory effect of tenascin on monocyte chemotaxis, allowing LTB4 stimulated monocytes to migrate through Matrigel/tenascin coated filters. In contrast, an antibody (LeuM5) directed against α_x (p150/95), a member of the β integrin family found on both PMNs and monocytes, did not reverse tenascin's inhibitory effect on LTB4-stimulated chemotaxis of PMN or monocytes through Matrigel/tenascin-coated filters (FIGS. 17A and 17B). As expected, monoclonal antibody IB4, directed against leukocyte β₂ integrins, inhibited chemotaxis of monocytes and PMNs across filters coated with Matrigel alone or with both Matrigel and tenascin. Thus, antibodies directed against members of the β₂ integrin family did not reverse tenascin's inhibitory effect on monocyte and PMN chemotaxis. These results indicate that blocking the interaction of monocytes or PMNs with tenascin, either by masking the tenascin on the matrix with F(ab)′₂ anti-tenascin or by blocking β₁ integrins on the cells, reversed the inhibitory effect of tenascin on monocyte and PMN chemotaxis.

Discussion

[0109] PMNs migrate through matrices formed by, and containing, proteins that are “normal” constituents of basement membranes and of the ground substance of interstitial spaces (e.g., collagens I and IV, laminin), in response to all chemoattractants tested (fMLP, TNF, C5a, IL-8, LTB4) (68, 69). In contrast, whether PMN migrate through matrices composed of, or containing, fibrin depends upon the specific chemoattractant with which they have been stimulated. For example, fMLP, TNF and C5a stimulate PMNs to adhere tightly to fibrin gels, but not to migrate into or through them. In contrast, IL-8 and LTB4 stimulate PMNs to migrate efficiently through these gels.

[0110] The capacity of specific chemoattractants to signal cessation of migration when PMNs contact fibrin suggested that this might be a mechanism by which these cells are excluded from some tissue compartments, and concentrated in others. One example, however, hardly establishes a general principle. Therefore, other matrix proteins that block PMN and monocyte chemotaxis were sought.

Tenascin Inhibits PMN and Monocyte Chemotaxis through Collagen I or Matrigel Matrices

[0111] Addition of tenascin to three-dimensional matrices formed by collagen I or Matrigel signals cessation of movement of PMNs and monocytes in response to all three chemoattractants tested (fMLP, LTB4, TNF) (FIGS. 11-17). The capacity of tenascin to block chemotaxis of PMNs stimulated by LTB4 is of special note since LTB4 promotes PMN migration through fibrin gels (25). This finding supports our contention that leukocyte migration through extracellular matrix is regulated by both the proteins in the matrix and the specific chemoattractant. It demonstrates that a chemoattractant can have entirely different effects on a single class of leukocyte, depending upon the matrix proteins with which the leukocyte is in contact.

One of Tenascin's Functions in Adults is to Inhibit PMN and Monocyte Entry into Specific Tissue Compartments

[0112] Tenascin is an unusual matrix protein. It is expressed widely in embryonic tissues where it regulates cell migration during organogenesis. Under physiological conditions in adults, tenascin is absent from most tissues, except lymphoid tissue (40, 55), and brain (43). However, under pathological conditions, tenascin synthesis is stimulated. It is deposited in the extracellular matrix in areas of vascular injury (57), and tumor stroma (43, 63), which are also areas of fibrin deposition (59, 70-73).

[0113] It is notable that tenascin and fibrin, matrix proteins deposited in and around diseased (e.g., malignant tumors), or injured tissues (e.g., atherosclerotic lesions), or areas in which T-cells concentrate (40, 43, 55, 57, 59, 63, 70-73), and chemically modified matrix proteins (e.g., non-enzymatically glycated collagen IV [74]), all signal phagocytic leukocytes to become sessile. Dvorak et al. (70), and Singh et al. (59) have presented evidence that tumor stroma protects the tumors from host immune effector cells. Viewed from this perspective, tenascin contributes to an immuno-inhibitory effect of tumor stroma.

β₁ Integrins Play No Role in PMN or Monocyte Migration through Matrigel

[0114] Anti-β₁ integrins had no inhibitory effect on PMN or monocyte chemotaxis through Matrigel alone (FIGS. 17A and 17B), while antibodies directed against PMN and monocyte β₂ integrins blocked PMN and monocyte chemotaxis under all circumstances tested (75), including through Matrigel (FIGS. 17A and 17B). These findings suggest that β₁ integrins play no role in PMN or monocyte chemotaxis through Matrigel. These studies did not examine whether antibodies directed against β₂ integrins inhibited PMN or monocyte chemotaxis through Matrigel by blocking their adhesion to the Matrigel or by other mechanisms, such as stimulating an increase in their cAMP content (76).

On the Mechanism(s) by which Tenascin Blocks PMN and Monocyte Chemotaxis

[0115] Chemoattractants that signal PMNs to remain sessile on fibrin gels, cause these cells to adhere more tightly and in greater numbers to fibrin than chemoattractants that promote PMN to migrate through fibrin gels. Similarly, chemoattractants stimulate monocytes to become sessile and adhere more tightly to glycated collagen IV than to native collagen IV (65, 74). In contrast, no increase in the number of chemoattractant-stimulated PMN or monocytes that adhered to tenascin-impregnated Matrigel over Matrigel alone was observed. Thus, while fibrin and glycated matrices may inhibit chemotaxis by providing ligands to which chemoattractant-stimulated PMNs and monocytes bind very tightly, and in increased numbers, tenascin appears to exert its inhibitory effect by a different mechanism.

[0116] β₁ integrins have been reported to promote adhesion of normal and transformed cells to tenascin (53, 54, 60). F(ab)′₂ anti-tenascin, and anti-β₁ integrins reversed tenascin's inhibitory effect on both PMN and monocyte chemotaxis (FIGS. 17A and 17B). Since β₁ integrins appear to play no role in PMN or monocyte chemotaxis through Matrigel, the most straightforward explanation for the capacity of F(ab)′₂ anti-tenascin and anti-β₁ integrins to block tenascin's inhibitory effect on chemotaxis, is that the interaction of β₁ integrins on PMN and monocytes with cognate ligands on tenascin signals these cells to stop migrating.

[0117] The results of Example 1 show that β₁ integrins regulate the migration of fMLP-stimulated PMNs through fibrin and that antibodies or peptides that block β₁ integrins allow all PMNs to migrate through fibrin gel in response to chemoattractant that otherwise would cause PMNs to stop migrating when they encounter fibrin. Further work is needed to identify the cellular pathways via which β integrins signal PMNs and monocytes to stop moving, and to determine the physiological significance of this event. Cellular pathways and physiological significance notwithstanding, one practical consequence of these findings is that antibodies vs PMN and monocyte 3 integrins may be therapeutically useful by facilitating entry of these cells into tissues and body compartments from which they otherwise are excluded.

[0118] Tenascin has domains (53), which are homologous to regions in epidermal growth factor, fibronectin, and fibrinogen. Since fibrin and tenascin block monocyte and PMN migration, tenascin's fibrinogen-like terminal knob may play a critical role in signalling leukocytes to stop migrating.

Example 3

[0119] The role of β₁ integrins in PMN chemotaxis through fibrin gels formed in cell culture insers (pore size=8 μm) has been examined. 10⁶ PMN were added to the upper compartment of the inserts and a chemoattractant was added to the lower compartment. Previous studies (Loike, et al., J. Exp. Med. 181: 1763, 1995) showed that PMN do not migrate through fibrin gels in response to a gradient FMLP but do so efficiently in response to a gradient of LTB4. In contrast, PMN migrate through collagen gels in response to either FMLP or LTB4. To determine the mechanism by which fibrin blocks PMN migration in response to FMLP, the effects of anti-integrin antibodies were tested. PMN incubated with anti-β₁ integrin antibodies (2 μg/ml) or the peptide GRGDSP (1 mg/ml), but do not GRGESP, migrated through fibrin gels in response to FMLP (FIG. 10B). Control experiments showed that anti-β₁ antibodies did not affect LTB4-stimulated PMN migration through fibrin. Furthermore, anti-α_v or anti-β integrin antibodies blocked PMN migration in response to either FMLP or LTB4 (FIG. 10A). These studies show that interactions between PMN β₁ integrins and matrix-associated ligands regulate PMN migration. They suggest that: 1) FMLP, but not LTB4, signals binding of β₁ integrins to β₁ lignads (e.g. RGD) on fibrin, 2) ligation of β₁ integrins signals FMLP-stimulated PMN to become sessile, and 3) chemoattractants signal PMN to crawl or to become sessile, depending upon the matrix proteins with which these cells are in contact.

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