Activation of complement by cell surface components of Staphylococcus aureus

Abstract

The abilities of intact S. aureus H, crude cell walls (CCW), purified cell walls (PCW, peptidoglycan [PG] and covalently linked teichoic acid), PG, and cell membranes (CM) to activate the complement system in normal human serum, C2[2nd component of complement]-deficient serum and immunoglobulin[Ig]-deficient serum were compared. On a weight basis, PCW was the most active fraction; intact organisms and CCW were about equally effective; and PG was least active in causing complement consumption in normal serum. CM also activated complement but did not give a clear dose-response relationship in the concentrations used. Kinetic studies revealed that C3-C9 consumption occurred at a significantly slower rate in C2-deficient serum, indicating that intact organisms, PCW and PG may activate the complement system via the classical and alternative pathways in normal serum. C3-C9 consumption was also slower in Ig deficient serum than in normal serum, implying that Ig play a role in attaining maximum rates of complement activation. In all sera studied, PG was less active in complement activation than PCW. A number of cell surface components of S. aureus can play a role in complement activation by this organism and the presence of teichoic acid has a significant enhancing effect in this regard.