FMLP- and TNF-stimulated monoclonal Lym-1 antibody-dependent lysis of B lymphoblastoid tumour targets by neutrophils

Human neutrophils, incubated with Cr(51)-labelled B lymphoblastoid Raji cells in the presence of the anti-target monoclonal antibody (mAb) Lym-1 plus formyl-methionyl-leucyl-phenylalanine (FMLP) or tumour necrosis factor alpha (TNF-α), were found to induce significant Cr(51) release, i.e. significant cytolysis. The lytic process was inhibited by mAb IV.3, specific for the Fcγ receptor (FcγR) type II. The mAb 3G8, which reacts with FcγR type III, was ineffective. Moreover, the lysis was inhibited by the anti-CD18 mAb MEM-48. These data suggest that FMLP/Lym-1 as well as TNF-α/Lym-1 cytolytic systems strictly require FcγRII and CD18 integrins. As the lysis induced by TNF-α/Lym-1 was prevented by pertussis toxin (PT), PT-sensitive G-proteins are likely to intervene in post-FcγRII signal transduction. Both the FMLP- and the TNF-α-dependent systems were also found to be equally susceptible to inhibition by various inhibitors of kinases (genistein, staurosporin, 1-(5-isoquinolinnylsulphonyl)-2-methylpiperazine and wortmannin). On the contrary, an inhibitor of protein kinase C (bis-indolyl-maleimide, BIM) was effective only in the FMLP/Lym-1 cytolytic system. Therefore, it appears that signals delivered by FMLP or TNF-α, BIM-sensitive and insensitive respectively, converge and synergize with those from G-protein-coupled FcγRII and, probably, CD18-integrins to promote the expression of the neutrophil cytolytic potential. © 1999 Cancer Research Campaign