Processing of streptococcal cell walls by rat macrophages and human monocytes in vitro

Phagocytosis and degradation of cell walls by peritoneal macrophages obtained from Fischer 344 or Buffalo rats was measured in tissue culture. Group A cell wall antigen, detected by immunofluorescence, persisted in cultured rat macrophages for at least 40 days, whereas group D cell wall material was eliminated by 6 to 8 days. This same pattern of persistence of group A cell walls and elimination of group D cell walls was observed in cultures of human monocytes followed for 24 days in culture. Group A streptococcal cell walls labeled with either [14C]alanine or [14C]glucose were handled in a similar manner by macrophages from either Fischer 344 or Buffalo rats. In contrast, [14C]glucose-labeled group D cell walls were degraded at a much faster rate. Buffalo macrophages were more efficient than Fischer 344 macrophages in degrading group D cell walls. The inability of macrophages to degrade group A cell walls was not due to a failure of lysosomes to fuse with phagosomes. Neither serum lysozyme in the culture medium nor cell wall-associated autolysin contributed to the degradation of group D cell walls by macrophages. Neither immune serum nor macrophages obtained from specifically immunized rats influenced phagocytosis or persistence of group A cell walls.