Factors in Human Serum Promoting Phagocytosis of Pseudomonas aeruginosa: II. Interaction of Opsonins with the Phagocytic Cell

Human polymorphonuclear leukocyte (PMN) receptors involved in opsonophagocytosis of Pseudomonas aeruginosa were studied. Opsonophagocytosis of bacteria preopsonized with specific IgG antibodies was inhibited by normal IgG but was not inhibited when the bacteria were preopsonized with specific IgG antibodies and complement. Trypsinized PMNs showed decreased phagocytic activity of bacteria preopsonized with IgG antibodies and complement, but phagocytosis of bacteria preopsonized with IgG antibodies alone was enhanced. The phagocytic activity of trypsinized PMNs was fully restored by addition of IgG antibodies to P. aeruginosa to the assays. The data suggest that cytophilic IgG antibodies act as the receptors for bacteria-antibody-complement complexes on human PMNs.