Modulation of complement fixation and the phlogistic capacity of group A, B, and D streptococci by human lysozyme acting on their cell walls.

Streptococci and streptococcal cell wall fragments induce arthritis in rats, with the severity and duration depending on the capacity of the cells or cell fragments to resist degradation by tissue enzymes. Their phlogogenic effects are apparently related to their ability to activate the alternate complement pathway (ACP). The in vitro activation of the ACP by lysozyme-treated cells and cell walls of group A, B, and D streptococci suggests that both rat and human lysozyme can modulate this activity, i.e., increasing it, decreasing it, or doing both in that order. The effects of the lysozymes also correlated with the degree to which they can unmask the aminosugar-reducing groups detectable in a given amount of cell wall, which suggests that partial depolymerization of the cell wall is critical for ACP activation. The effects of mutanolysin and C phage lysin on ACP activation were found to be correlated with their action on streptococcal cell walls. Neuraminidase had relatively little effect on ACP activation by most streptococcal strains tested. We conclude that the participation of tissue enzymes, including but not necessarily limited to lysozyme, is an important determinant for the clinical arthritis induced by group A, B, or D streptococci. Experimental arthritis induced in rats with whole (or disrupted) streptococci may depend both on the capacities of the cell walls to activate the ACP and on the capacities of the host tissue enzymes to modulate this activation. Great severity and long durations of the disease were determined by the capacity of the enzymes to degrade cell wall antigens to a degree sufficient to ensure efficient activation of the ACP without completely degrading the material so that it no longer activates complement. In this model, the limited resistance of group B peptidoglycan to lysozyme was a critical pathogenic factor.