Prostaglandin-mediated suppression of macrophage phagocytosis of Listeria monocytogenes

Suppression of macrophage phagocytosis of Listeria monocytogenes has been shown to be due to a low-molecular-weight component of spleen cell culture supernatant. The possibility that the factor could be a prostaglandin was investigated. When murine peritoneal macrophages were treated with prostaglandin E2 (PGE2), L. monocytogenes was phagocytized at a rate comparable to that phagocytized when treated with a low-molecular-weight fraction of concanavalin A-generated spleen cell culture supernatant. Suppressive activity of the spleen cell culture supernatant was abrogated when supernatant was prepared in the presence of indomethacin, a prostaglandin synthetase inhibitor. Prostaglandins were identified in supernatants with thin-layer and high-pressure liquid chromatography. These results suggest a role for prostaglandins, particularly PGE2, as a modulator of macrophage phagocytosis of L. monocytogenes.