Mouse peritoneal macrophages exposed to type-specific polysaccharide and peptidoglycan (PPG) from group A streptococci undergo marked morphologic and biochemical changes. The cells show increases in size and an increased number of lysosomes as demonstrated by vital staining with acridine orange. There are significant elevations in the levels of both lysosomal and nonlysosomal enzymes. Higher doses of PPG cause selective release of the hydrolases into the extracellular environment with no detectable loss of cell viability. The in vitro phenomena may be relevant to understanding the role of macrophages in chronic inflammation.

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