REGULATION OF PHAGOCYTOSIS AND [CA2+]I FLUX BY DISTINCT REGIONS OF AN FC RECEPTOR

The binding of multivalent immunoglobulin G complexes to Fc receptors (Fc-gamma-Rs) on macrophages activates multiple immune functions. A murine macrophage cell fine, but not a fibroblast cell line, that was transfected with human Fc-gamma-RIIA mediated phagocytosis and an intracellular Ca2+ concentration ([Ca2+]i) flux upon cross-linking of human Fc-gamma-RIIA. Transfected macrophages that expressed a truncated receptor lacking 17 carboxy-terminal amino acids phagocytosed small antibody complexes. However, only wild-type transfectants phagocytosed labeled erythrocytes and fluxed [Ca2+]i. Thus, the cytoplasmic domain of human Fc-gamma-RIIA contains distinct functional regions.