IN NEUTROPHILS THE BINDING TO IMMUNOCOMPLEXES INDUCES THE TYROSINE PHOSPHORYLATION OF FC-GAMMA-RII BUT THIS PHOSPHORYLATION IS NOT AN ESSENTIAL SIGNAL FOR FC-MEDIATED PHAGOCYTOSIS

It has been recently suggested that protein tyrosine phosphorylation i s involved in Fc gamma Rs-mediated signalling. In this paper we have i nvestigated if in human neutrophils a tyrosine phosphorylation of F ga mma RII takes places after the binding with immunocomplexes and if thi s phosphorylation plays a role in phagocytic signal. The immunoprecipi tation with mAb anti-Fc gamma RII of lysates of neutrophils challenged in suspension with insoluble immunocomplexes (IIC) or sheep erythrocy tes opsonized with IgG (E-IgG), followed by immunoblotting with anti-p hosphotyrosine antibody, demonstrated that Fc gamma RII was tyrosine p hosphorylated. When neutrophils were pretreated with different doses o f tyrosine kinase inhibitors, genistein or erbstatin, the phosphorylat ion of Fc gamma RII induced by IIC or E-IgG was dose dependently inhib ited. In these conditions both genistein and erbstatin failed to inhib it the phagocytosis of E-IgG. These results demonstrated that in human neutrophils in suspension the binding to Pc of IgG induces a tyrosine phosphorylation of Fc gamma RII but this phosphorylation is not an es sential signal for phagocytosis of IgG-opsonized particles. (C) 1994 A cademic Press, Inc.