Effect of antibodies and complement on the interaction between Escherichia coli 0111:B4 and polymorphonuclear leukocytes

The interaction of Escherichia coli 0111:B4 with polymorphonuclear leukocytes in the presence of specific antibodies and complement was studied. This strain, which is resistant to phagocytosis by polymorphonuclear leukocytes, may be ingested and killed by the phagocytes in the presence of both antibodies and fresh serum. The ineffectiveness of fresh serum to promote ingestion of E. coli 0111:B4 by the phagocytes in the absence of antibodies reflects the inability of this strain to activate the complement system through the alternative pathway. Investigation of the mechanisms of the bacterial killing by polymorphonuclear leukocytes showed that both antibodies and complement were required for the oxygen-independent bactericidal system, whereas they were not needed for the oxygen-dependent system.