Group A streptococci and their isolated cell walls, normally resistant to egg-white lysozyme and the lysosomal enzymes of human phagocytes, were converted to lysozyme-sensitive forms by partial removal of cell wall carbohydrate, substitution of free amino groups, and by saponification of O-acyl groups. The resultant modified streptococcal cell walls showed rapid degradation when treated with leukocyte granule extract derived from human peripheral blood polymorphonuclear leukocytes and monocytes and when subjected to phagocytosis by living human leukocytes. These results indicate that the factors responsible for lysozyme resistance of the group A cell wall also influence its resistance to human leukocyte granule enzymes and suggest that the chemical composition of the cell wall, in addition to the presence of cell wall carbohydrate, determines this resistance.
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