Absorption of blocking activity from human tumor-bearer sera by Staphylococcus aureus, Cowan I

Staphylococcus aureus, strain Cowan I, contains a cell-wall substance, protein A, which combines with the Fc part of IgG in most mammalian species. It can therefore be used as a solid-phase immunoabsorbant for elimination of the reacting immunoglobulins. Since it has been shown that Cowan I could absorb out the blocking activity of sera from rats bearing isografts of polyoma-virus-induced sarcomas or chemically induced colon carcinomas, we investigated what effects Cowan I absorption of human tumor-bearer sera might have. In all tumor-bearer sera tested, from patients with melanomas or colon carcinomas, treatment with protein-A-containing staphylococci decreased the sera's ability to inhibit lymphocyte-mediated cytotoxicity in vitro. Cowan-I-treated sera from healthy controls had no effect on lymphocyte cytotoxicity. Nor did Cowan-I-treated tumor-bearer sera potentiate or "arm" normal lymphocytes against tumor target cells. There was no evidence of complement-dependent cytotoxicity with added human complement in sera from melanoma and colon carcinoma bearing patients either before or after absorption with Staphylococcus aureus, Cowan I, The concentrations of IgA, IgG and IgM were determined in sera used for in vitro tests of blocking activity and complement-dependent cytotoxicity before and after absorption. No reduction of IgA, reduction to undetectable levels of IgG and 20-30 percent reduction of IgM immunoglobulins as compared to unabsorbed sera were demonstrated.