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 cell s in the presence of the anti-target monoclonal antibody (mAb) Lym-1 plus f ormyl-methionyl-leucyl-phenylalanine (FMLP) or tumour necrosis factor alpha (TNF-alpha), were found to induce significant Cr-51 release, i.e, signific ant cytolysis. The lytic process was inhibited by mAb IV.3, specific for th e Fc gamma receptor (Fc gamma R) type II. The mAb 3G8, which reacts with Fc gamma R type ill, was ineffective. Moreover, the lysis was inhibited by th e anti-CD18 mAb MEM-48. These data suggest that FMLP/Lym-1 as well as TNF-a lpha/Lym-1 cytolytic systems strictly require Fc gamma RII and CD18 integri ns. As the lysis' induced by TNF-alpha/Lym-1 was prevented by pertussis tox in (PT), PT-sensitive G-proteins are likely to intervene in posl-FcyRII sig nal transduction. Both the FMLP- and the TNF-alpha-dependent systems were a lso found to be equally susceptible to inhibition by various inhibitors of kinases (genistein, staurosporin, 1-(5-isoquinolinnylsulphonyl)-2-methylpip erazine 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-alpha, BIM-sensitive and insensitive respectively, converge and synergize with th ose from G-protein-coupled Fc gamma RII and, probably, CD18-integrins to pr omote the expression of the neutrophil cytolytic potential.