Alteration of in vitro anti-tumor activity of tumor-bearer sera by absorption with Staphylococcus aureus, Cowan I.

Abstract

AbstractStaphylococcus aureus, strain Cowan I, has been shown to contain a cell‐wall substance, protein A, which combines with the Fc part of IgG in most mammalian species. Since the blocking activity of sera from tumor‐bearing individuals has previously been found to be associated with 7S immunoglobulins, it was investigated whether Cowan I could absorb out the blocking activity of sera from rats carrying either isografted polyoma virus induced sarcomas or chemically induced colon carcinomas. In all sera tested, treatment with protein A abrogated the sera's ability to inhibit lymphocyte‐mediated cytotoxicity in vitro. Absorption of sera with Staphylococcus aureus, strain Wood 46, not containing protein A, had no effect on the blocking activity. Admixtures of protein‐A‐treated blocking sera to untreated blocking sera from animals bearing the same tumor type, specifically abrogated the blocking activity, while admixture of Wood 46 absorbed sera, protein‐A‐treated normal sera, or protein‐A‐treated sera from animals bearing a different tumor type did not cause a similar abrogation. The blocking sera from tumor‐bearing rats were not cytotoxic to their specific tumor target cells in the presence of homologous complement. After protein A treatment, serum from rats bearing isografts of sarcomas induced by polyoma virus showed specific complement‐dependent cytotoxicity to polyoma tumor target cells. Serum from primary colon carcinoma bearing rats also had complement‐dependent cytotoxic effect on colon tumor target cells after protein A treatment. Sera used for in vitro tests of blocking activity and complement‐dependent cytotoxicity were analyzed for IgG concentration before and after absorption with S. aureus, Cowan I. A 20‐30% reduction of IgG class immunoglobulins as compared to unabsorbed or control (Wood 46) treated sera was demonstrated.