Opsonic activity of fibronectin in the phagocytosis of Staphylococcus aureus by polymorphonuclear leukocytes.

The effect of the opsonic activity of human purified fibronectin on phagocytosis of Staphylococcus aureus by human polymorphonuclear leukocytes was investigated. After opsonization with fibronectin there was a significant increase in the rate of phagocytosis of four out of six Staphylococcus aureus strains. Both attachment to and ingestion by leukocytes was affected, as revealed by lysostaphin treatment. Incubation of leukocytes with fibronectin prior to phagocytosis did not enhance the phagocytosis of Staphylococcus aureus. This shows that the observed enhancement of phagocytosis was dependent on the binding of fibronectin to Staphylococcus aureus. The ability of fibronectin to opsonize different strains of Staphylococcus aureus varied with the strain. A variation was also observed in fibronectin-induced phagocytosis by leukocytes from different donors.