title: Opsonin-independent ligation of Fc gamma receptors. The 3G8-bearing receptors on neutrophils mediate the phagocytosis of concanavalin A-treated erythrocytes and nonopsonized Escherichia coli.
abstract: We report that phagocytosis by human neutrophils of Con A-treated erythrocytes (E-Con A) and nonopsonized Escherichia coli with mannose-binding adhesions is mediated by the Fc gamma receptor bearing the 3G8 epitope. Modulation of Fc receptors by pretreating with aggregated-IgG or with 3G8 anti-Fc gamma receptor mAb markedly inhibited internalization of E-Con A and E. coli without altering their cell surface attachment. Phagocytosis of these probes was specifically blocked by alpha-methylmannoside and D-mannose and not by other monosaccharides. Thus, recognition of E-Con A and E. coli by the Fc receptor is dependent upon the mannose-specific interaction with lectin or lectin-like adhesions. These data demonstrate that ligands other than the classical IgG opsonins can bind to classical immune receptors for IgG through lectin-carbohydrate interactions.
mesh_terms: D003208:Concanavalin A; D004705:Endocytosis; D000939:Epitopes; D004912:Erythrocytes; D004926:Escherichia coli / Q000276:immunology; D006023:Glycoproteins / Q000502:physiology*; D006801:Humans; D066298:In Vitro Techniques; D008562:Membrane Glycoproteins; D009504:Neutrophils / Q000502:physiology*; D009895:Opsonin Proteins; D010587:Phagocytosis; D011961:Receptors, Fc / Q000276:immunology / Q000502:physiology*; D017452:Receptors, IgG
chemical_list: D000939:Epitopes; D006023:Glycoproteins; D008562:Membrane Glycoproteins; D009895:Opsonin Proteins; D011961:Receptors, Fc; D017452:Receptors, IgG; C025363:mannoproteins; D003208:Concanavalin A