DETECTION OF SOLUBLE TUMOR-ASSOCIATED ANTIGENS IN SERUM OF TUMOR-BEARING RATS AND THEIR IMMUNOLOGICAL ROLE INVIVO

  • 1 January 1977
    • journal article
    • research article
    • Vol. 37  (9) , 3385-3389
Abstract
Circulating soluble tumor antigens were detected in the serum of tumor-bearing rats. Sublethally irradiated W/Fu rats inoculated with syngeneic C58(NT)D Gross virus induced lymphoma served as the source of tumor antigens. Soluble antigens were assessed by specific inhibition of complement mediated cytotoxicity of isogenic W/Fu anti-C58(NT)D antibodies against 51Cr tumor target cells. With a s.c. inoculum of 5 .times. 107 tumor cells, circulating tumor antigens were first detected at day 8, and a maximum concentration was reached by days 13-14, which coincided with the peak of tumor growth and was followed by sudden death of the animals. Pooled serum from tumor-bearing rats was fractionated on Sephadex G-150 and resulted in 1 peak that contained all of the antigenic activity. The molecular weight of this fraction was estimated to be 50,000-60,000 daltons. Presensitization of normal rats with soluble tumor antigens resulted in a specific acceleration of tumor growth and delay in tumor rejection. Specificity was shown by lack of C58(NT)D tumor enhancement in rats presensitized with serum containing tumor antigens from a syngeneic but antigenically unrelated WR-6 lymphoma. The biological significance of circulating soluble tumor antigen mediating specific immunosuppression against an immunogenic tumor is discussed.