FC gamma receptor mediated phagocytosis by human neutrophil cytoplasts

Neutrophils utilize Fcgamma Receptors (FcgammaR) to bind and internalize antibody coated cells or immune complexes. We have compared ultrastructurally FcgammaR-mediated phagocytosis by neutrophil cytoplasts (enucleated and granule-free neutrophils) prepared either by treatment with cytochalasin B (CB-cytoplasts) followed by ultracentrifugation or by brief heating at 45 degrees C in suspension followed by ultracentrifugation. The phagocytosis of antibody-coated erythrocytes (EIgG) or the internalization of crosslinked IgG complexes by cytoplasts prepared by brief heating was comparable to that of untreated neutrophils. In contrast, CB-cytoplasts bound but failed to internalize ElgG or crosslinked IgG complexes. Comparison of these two methods for the preparation of neutrophil cytoplasts may assist in clarifying the signal transduction requirements involved following ligand binding to FcgammaR which initiate phagocytosis.