Leukocyte chemosensory migration on vascular prosthetic biomaterial is mediated by an integrin β2 receptor chain

The ability of adherent activated leukocytes to migrate on implanted prosthetic biomaterial surfaces may be an early rate-limiting step in eliminating periprosthetic infection. The goal of this study was to explore the molecular mechanism governing leukocyte migration on the implantable cardiovascular prosthetic biomaterial, expanded polytetrafluoroethylene (ePTFE), in response to stimulation by the soluble chemokine, N-formyl-methionyl-leucyl-phenylalanine (fMLP). We used a population level migration assay to study the migration of polymorphonuclear leukocytes (PMN) on ePTFE, overlaid by a gelatin/agar composite. A theoretical random walk model was applied to describe fMLP-induced PMN migration on ePTFE in terms of an objective random cell migration coefficient, μ. Our results show that following stimulation with 0–10−7 fMLP, the value of μ ranged from 5.43×10−9 to 1.08×10−7 cm2/s, with a maximum value obtained at 10−8 fMLP. We probed the expression levels of various β2 integrin receptor subunits and their contribution to the migratory function of ePTFE-adherent PMN over a wide range of fMLP concentration. We found that the expression of the integrin β-chain, CD18, was also maximized at 10−8 fMLP, along with only slight changes in the expression of integrin α-chains (CD11a,b,c). We report that treatment with antibodies against either β or combined α chains, but not individual α chains, inhibited PMN attachment to ePTFE at 10−8 fMLP, suggesting the likely role of combined β2 receptor subunits in early adhesion events following stimulation. However, treatment with only anti-CD18 significantly lowered PMN migration on ePTFE (μ=5.98×10−9 cm2/s), and this degree of inhibition was much greater than that elicited by the combined treatment with antibodies recognizing all possible α-chains. Overall, we conclude that migratory behavior of chemokinetically stimulated PMN on ePTFE is mediated by the integrin β chain pool, and is only weakly regulated by the integrin α chain.