Evidence that TNF-induced respiratory burst of adherent PMN is mediated by integrin alpha sub(L) beta sub(2)

Polymorphonuclear leukocytes (PMN) respond to tumor necrosis factor (TNF) with a respiratory burst (RB) only after adherence to surfaces coated with extracellular matrix proteins such as fibronectin and fibrinogen (permissive substrates) but not with others such as laminin or collagen (nonpermissive substrates). As PMN adherence to both types of surfaces is dependent on beta sub(2) integrins, we investigated the molecular basis of the different metabolic response to TNF. In particular, we evaluated the relative role of each beta sub(2) integrin ( alpha sub(L) beta sub(2), alpha sub(M) beta sub(2), and alpha sub(X) beta sub(2)) in adherence and O super(-) sub(2) production of PMN residing on fibronectin- and laminin-coated surfaces, which were considered as models of permissive and nonpermissive surfaces, respectively. By using alpha chain-specific monoclonal antibodies (mAb), we show that alpha sub(M) beta sub(2) and alpha sub(X) beta sub(2) mediate adherence to fibronectin and laminin; alpha sub(L) beta sub(2) is not involved in adherence to laminin and has only a minimal contribution in adherence to fibronectin. Furthermore, production of O super(-) sub(2) in response to TNF was induced by immobilized anti- alpha sub(L) beta sub(2) but not anti- alpha sub(M) beta sub(2) or anti- alpha sub(X) beta sub(2) mAb. A strong correlation was also found between expression of alpha sub(L) beta sub(2) and TNF-induced RB on fibronectin. Lastly, PMN responded to TNF on laminin with a RB after the inclusion of alpha sub(L)-specific mAb in the laminin coat. Thus, we conclude that TNF-induced RB by PMN residing on fibronectin is mediated by alpha sub(L) beta sub(2) and that alpha sub(M) beta sub(2) and alpha sub(X) beta sub(2) are likely to play an ancillary role to the signaling activity of alpha sub(L) beta sub(2) by facilitating its recruitment to sites of adherence. The nonpermissiveness of laminin appears to be a consequence of its inability to act as a ligand for alpha sub(L) beta sub(2).