Effects of fibronectin on the interaction of polymorphonuclear leukocytes with unopsonized and antibody-opsonized bacteria.

Fibronectin (Fn) affects the interaction of polymorphonuclear leukocytes (PMNLs) with certain bacteria. Fn alone enhanced the response, in a chemiluminescence (CL) assay, of PMNLs to Staphylococcus aureus (P less than .05) and Staphylococcus epidermidis (P less than .01) but had no effect on type III, group B streptococci (GBS) or Escherichia coli. When GBS or E. coli were first preopsonized in antibody, Fn significantly enhanced the CL response of PMNLs (P less than .05). The intracellular metabolic inhibitor NaN3 but not the extracellular scavengers superoxide dismutase or human serum albumin inhibited Fn-enhanced CL; this fact suggests that enhancement of the respiratory burst by Fn is an intracellular event. We used an acridine orange-crystal violet monolayer assay to examine the effects of Fn on ingestion and intracellular killing of bacteria by PMNLs. Fn alone promoted uptake and killing of S. aureus (P less than .01) and S. epidermidis (P less than .05) by PMNLs but did not enhance monolayer phagocytosis of GBS or E. coli, unless these bacteria were preopsonized in antibody (P less than .01).