Fibronectin mediates attachment of Staphylococcus aureus to human neutrophils.

Plasma fibronectin binds to gelatin and is thought to mediate the removal of blood-borne particles by the reticuloendothelial system. This removal has primarily been studied using gelatin-coated colloidal particles. Fibronectin also binds to gram-positive bacteria. We tested the possibility that fibronectin might act as an opsonin for phagocytosis of bacteria by neutrophils. When fibronectin in physiologic concentrations was present in reaction mixtures containing Staphylococcus aureus and human neutrophils, staphylococci adhered to. but were not ingested by, neutrophils. Chemiluminescence of . mixtures of neutrophils and S. aureus was enhanced by fibronectin. Although S. aureus were not killed by attachment, the number of colony-forming units fell as the bacteria were concentrated on the neutrophil surfaces. Washing of the neutrophils did not remove attached staphylococci. Sonication, however,