Tyrosine phosphorylation and its possible role in superoxide production by human neutrophils stimulated with FMLP and IgG.

Superoxide production by human neutrophils stimulated with FMLP and soluble aggregated human IgG were inhibited in a dose dependent manner by two kinds of tyrosine kinase inhibitors, erbstatin and genistein. Superoxide production stimulated with surface bound IgG, however, was scarcely inhibited by either inhibitor. Protein tyrosine phosphorylation studies with immunoblotting revealed specific tyrosine phosphorylation of a 40 Kd protein by soluble aggregated and surface bound IgG, and that of a 39 Kd protein, as well as the 40 Kd protein, by FMLP. These were all inhibited by the tyrosine kinase inhibitors. These data suggest that superoxide production induced by FMLP and soluble aggregated IgG are, at least in part, tyrosine kinase dependent, but the tyrosine kinases and/or substrates of tyrosine kinases involved may be different. In addition, tyrosine kinase independent pathways are also suggested to be involved in superoxide production by stimulation with surface bound IgG.