C5a-stimulated human neutrophils use a subset of β2 integrins to support the adhesion-dependent phase of superoxide production

Isolated human polymorphonuclear neutrophils (PMN) responded to human C5a with an immediate, transient release of superoxide lasting from 0.5 to 5 min. This was followed by a second release of superoxide, which began at 10 min after addition of C5a, was sustained for more than 30 min, and required ICAM-1 immobilized in the wells. F(ab')(2) monoclonal antibody (mAb) preparations were used to dissect the role of individual beta (2) integrins and to avoid the confounding effects of ligating Fe receptors. Anti-CD18 mAb treatment of the. PMN had no effect on the immediate first phase but completely inhibited the second, adhesion-dependent phase of superoxide production. Anti-CR3 mAb only inhibited the adhesion phase of superoxide production partially, implying that other beta (2) integrins were involved. A mixture of anti-CD11a, anti-CD11b, and anti-CD11c was not able to block superoxide production completely, suggesting a role for alphad/beta (2). Surprisingly, blocking anti-LFA-1 mAb had no effect on superoxide production. Consistent with this observation, immobilized, purified ICAM-2, a specific counter-receptor for LFA-1, did not support the adhesion-dependent phase of superoxide production. Thus, PMN treated with C5a used signals via CR3, P150/95, and alphad/beta (2), but not LFA-I, to support superoxide production. LFA-1 has been shown by others to mediate most of the adhesion necessary for transendothelial migration in vivo. The inability of LFA-1 ligation to stimulate superoxide production may be an important means of preventing Mood-vessel damage when PMN migrate across the endothelium.