C5a-stimulated human neutrophils use a subset of beta(2) integrins to support the adhesion-dependent phase of superoxide production

Isolated human polymorphonuclear neutrophils (PMN) responded to human C5a w ith 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 mi n after addition of C5a, was sustained for more than 30 min, and required I CAM-1 immobilized in the wells. F(ab')(2) monoclonal antibody (mAb) prepara tions were used to dissect the role of individual beta (2) integrins and to avoid the confounding effects of ligating Fe receptors. Anti-CD18 mAb trea tment of the. PMN had no effect on the immediate first phase but completely inhibited the second, adhesion-dependent phase of superoxide production. A nti-CR3 mAb only inhibited the adhesion phase of superoxide production part ially, implying that other beta (2) integrins were involved. A mixture of a nti-CD11a, anti-CD11b, and anti-CD11c was not able to block superoxide prod uction completely, suggesting a role for alphad/beta (2). Surprisingly, blo cking anti-LFA-1 mAb had no effect on superoxide production. Consistent wit h this observation, immobilized, purified ICAM-2, a specific counter-recept or for LFA-1, did not support the adhesion-dependent phase of superoxide pr oduction. Thus, PMN treated with C5a used signals via CR3, P150/95, and alp had/beta (2), but not LFA-I, to support superoxide production. LFA-1 has be en shown by others to mediate most of the adhesion necessary for transendot helial migration in vivo. The inability of LFA-1 ligation to stimulate supe roxide production may be an important means of preventing Mood-vessel damag e when PMN migrate across the endothelium.