Opsonic requirements for staphylococcal phagocytosis. Heterogeneity among strains

Efficient phagocytosis of staphylococci by human neutrophilis is dependent on bacterial opsonization by serum factors. These factors include specific antibodies as well as components of the classical and alternative complement systems. In this study the opsonic requirements of three strains of S. aureus and three strains of S. epidermidis were investigated by incubating [3H]thymidine-labelled bacteria in sera with different opsonic activities and measuring rates of phagocytosis by human neutrophils. Opsonization of S. aureus Cowan I and 502 A depended primarily on activation of the classical complement pathway. Effective opsonization occurred in the absence of immunoglobulin but not in the absence of complement. A protein A deficient mutant of S. aureus Cowan I was poorly opsonized in the absence of IgG, however. S. aureus Wood 46 and two strains of S. epidermidis were opsonized primarily through the alternative complement pathway and depended on the presence of serum IgG. A third S. epidermidis strain was efficiently opsonized in heat-inactivated serum without complement activity. Thus, a heterogeneity of opsonic requirements was found among staphylococcal strains. It is proposed that cell wall protein A may be an important determinant of this heterogeneity.