EFFECTS OF PLATELET-RELEASE PRODUCTS ON NEUTROPHILIC FC-GAMMA RECEPTORS

Large and small macromolecular activators of phagocytosis from platele ts (l-MAPP and s-MAPP, respectively), which function via the neutrophi lic Fc gamma receptors (Fc gamma R) were refined from platelet release products by gel filtration and affinity chromatography,vith the use o f an anti transferrin antibody column and the mechanism of phagocytosi s activation was investigated. Flow cytometry revealed that l-MAPP and s-MAPP did not increase the expression of neutrophilic Fc gamma RII ( CD32) and Fc gamma RIII (CD16) antigens, whereas rosette formation of neutrophils with rabbit IgG-sensitized sheep erythrocytes (EA) in the presence of anti Fc gamma R antibodies suggested that both MAPPs incre ase the binding ability of Fc gamma RII, On the other hand, the enhanc ing effect of l-MAPP and s-MAPP on neutrophilic phagocytosis disappear ed with the increase in phagocytosis by the phosphate-buffered saline control neutrophils when they were centrifuged with EA before incubati on for phagocytosis. The enhanced phagocytosis, both by the two MAPPs and centrifugation, was canceled by treatment of the neutrophils with anti-CD32 Fab. The phagocytosis activatory effects of MAPP on neutroph ils were canceled by anti-CD71 monoclonal antibody but not by transfer rin.