Effect of lipopolysaccharide on the stimulation of macrophage Fc-dependent phagocytosis by splenic B lymphocytes.

Macrophage phagocytic activity is regulated by a variety of products derived from activated lymphocytes. It has been reported that nonactivated splenic B and T lymphocytes enhance macrophage glucose metabolism. In addition, the enhancement of macrophage glucose metabolism was further increased by direct effects of bacterial lipopolysaccharide (LPS) on B, but not T, lymphocytes. In the present study, the effect of purified murine splenic B and T lymphocytes on Fc-dependent phagocytosis by thioglycollate-elicited peritoneal macrophages in the presence or absence of LPS has been investigated. Fc-dependent phagocytosis was assayed by measuring the ingestion of 51Cr-tagged sheep erythrocytes. After 3 or 4 days in culture, nonadherent spleen cells (NASC) and B and T lymphocytes from C3H/HeN (LPS-responder) mice produced 92 +/- 27%, 83 +/- 13%, and 147 +/- 33% increases in C3H/HeJ (LPS-hyporesponder) macrophage phagocytic activity, respectively. A similar effect was observed in Balb/c mice. Cell-free supernatant from NASC and B lymphocytes precultured for 2 or 4 days produced a 74 +/- 20% and 157 +/- 42% increase in phagocytosis respectively. At concentrations which have been previously shown to markedly enhance the ability of splenic B lymphocytes to stimulate macrophage glucose metabolism, Escherichia coli K235 LPS (10 micrograms/ml) did not alter the stimulatory effects of any of the splenic lymphocyte populations on macrophage Fc-dependent phagocytosis. These data suggest that B lymphocytes produce a soluble factor(s) which stimulates macrophage phagocytosis. In addition, LPS has different effects on the regulation of macrophage phagocytic activity and metabolism by B lymphocytes.