Increased phagocytic activity of splenectomized mice challenged with Listeria monocytogenes

Adult splenectomized mice exhibit increased resistance to infection with Listeria monocytogenes. Phagocytosis, by reticulo-endothelial cells, of test particles (51Cr-labelled sheep erythrocytes) is the same in splenectomized and control mice. However, 24 h exposure to Listeria, which fails to influence phagocytic activity of normal mice, greatly enhances the blood clearance and liver uptake of the test particles in splenectomized mice. The presence of a cell population and/or product in the spleen which modulates macrophage activation upon the exposure to appropriate stimuli is postulated.