Factors in Human Serum Promoting Phagocytosis of Pseudomonas aeruginosa. I. Interaction of Opsonins with the Bacterium

Factors in normal human serum that are required for opsonophagocytosis and intracellular killing of Pseudomonas aeruginosa by human polymorphonuclear leukocytes were investigated. IgG natural antibodies, properdin, and the proactivator of the third component of complement were found to be essential to these events. The addition of immune IgG antibodies to the system eliminated the requirement for properdin and the proactivator. These observations suggest that two mechanisms of complement activation can be involved in opsonophagocytosis of P. aeruginosa.