Fibronectin enhances respiratory burst of phagocytes stimulated by zymosan and immune complexes.

Plasma fibronectin (FN) has been demonstrated to serve as an opsonin involved in the ingestion of foreign particles by phagocytes. This study concerns the effect of FN exposure on the respiratory burst of normal human peripheral phagocytes, using a luminol-dependent chemiluminescence (CL) assay for measurement of reactive oxygen metabolites generated. FN enhanced, in a dose-dependent manner, the CL response of circulating monocytes stimulated, probably via beta-glucan receptor, with unopsonized zymosan. FN also increased the CL response of phagocytes to fresh serum-opsonized zymosan. When we used a glycolipid (ceramide pentasaccharide, CPS) incorporated on liposome membranes as an antigen, the immune complexes prepared between CPS and human IgG (as antibody) did not induce a CL response, differing from previous reports. Addition of FN to the immune complexes significantly enhanced the CL response of phagocytes. The role of FN in host defence is discussed.