The role of Staphylococcus aureus cell-wall peptidoglycan, teichoic acid and protein A in the processes of complement activation and opsonization.

The role of cell-wall peptidoglycan, teichoic acid and protein A in the processes of Staphylococcus aureus complement activation and opsonization was investigated. CH50 consumption studies reveal that, although all cell-surface fractions were capable of activating the classical C pathway, only peptidoglycan consumed C via the alternative pathway. Using a quantitative immunofluorescence assay, peptidoglycan was shown to bind C3 molecules via the classical as well as via the alternative C pathway and in the absence of IgG and IgA class antibodies. C activation via the classical and the alternative pathway could be distinguished by kinetic analysis. By comparing the rates of staphylococcal C consumption, C3 fixation and opsonization it was found that the CH50 consumption assay is a relatively insensitive method and may yield results that do not necessarily reflect the process of bacterial opsonization.