title: Contribution of immunoglobulins M and G, complement, and properdin to the intracellular killing of Escherichia coli by polymorphonuclear leukocytes.
abstract: The effect of immunoglobulins and complement (C) on phagocytosis and intracellular killing of Escherichia coli was studied in vitro. The incubation system consisted of monolayers of human polymorphonuclear leukocytes and C-resistant, [3H]thymidine-labeled E. coli C source was human serum deprived of immunoglobulins and properdin by immunoabsorption. In the absence of C, only immunoglobulin G-coated bacteria were phagocytosed, whereas immunoglobulin M lacked opsonic activity. In the presence of C, phagocytosis was enhanced; however, immunoglobulin M was now more efficient than immunoglobulin G. Intracellular killing was notably augmented when C was activated by immunoglobulin G- or immunoglobulin M-coated bacteria; in contrast, the alternative activation of C by properdin had no effect on phagocytosis or intracellular killing. These results demonstrate the importance of immunoglobulins together with C not only for phagocytosis but also for efficient intracellular killing.
mesh_terms: D002478:Cells, Cultured; D003176:Complement C3; D003165:Complement System Proteins; D004926:Escherichia coli / Q000276:immunology*; D006801:Humans; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D009504:Neutrophils / Q000276:immunology*; D010587:Phagocytosis; D011414:Properdin
chemical_list: D003176:Complement C3; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D011414:Properdin; D003165:Complement System Proteins