Inhibition of macrophage phagocytic activity by group A streptococcal cell walls

Group A streptococcal cell walls inhibited phagocytosis of polystyrene latex particles by rat peritoneal macrophages in vitro. This inhibition was not accompanied by a measurable loss of cell viability. Group D streptococcal cell walls were relatively ineffective in altering phagocytosis. The effectiveness of group A variant streptococcal cell walls and peptidoglycan derived from group A cell walls was increased if cell wall preparations were added to macrophage cultures 12 h before, rather than simultaneously with, latex particles.