Tumor immunity to murine plasma cell tumors. V. Demonstration of a unique tumor antigen that is not associated with the myeloma idiotype.

Abstract

AbstractA plasma‐cell tumor, Cl.18 of C3H/He derivation, exhibits a unique tumor‐associated antigen (TAA) which is detectable both in vitro and also as a tumor‐associated transplantation antigen (TATA) in vivo. Immunoglobulin idiotypic determinants have been thought to be prominent TATAs. Studies were performed to determine whether the unique TAA of Cl. 18 is its immunoglobulin idiotypic determinant. Mice immunized with CI. 18 myeloma protein (CI.18 MP) exhibit some protection to subsequent challenge with Cl. 18 tumor cells indicating that the CI.18 idiotypic determinant can indeed act as a weak TATA. However, in vitro lysis of CI. 18 tumor cells by cytotoxic T cells induced in vitro to CI. 18‐unique TAA is not blocked by CI. 18 MP, either in soluble form or when bound to sheep red blood cells. Spleen cells from mice immunized to CI. 18 MP in vivo do not undergo a secondary cytotoxic response when stimulated in vitro by CI.18 tumor cells. When C3H mice are immunized with tumor cells they are highly resistant to a subsequent challenge with CI. 18 tumor cells, and spleen cells from these mice show a marked secondary cytotoxic response when stimulated in vitro by CI. 18 tumor cells. Spleen cells from these mice, however, do not mount a secondary cytotoxic response when stimulated with CI.18 MP in vitro. We conclude that the unique TAA present on CI.18 cells is not the idiotypic immunoglobulin determinant, although both antigens can act as TATA in vivo. These studies support the view that although some plasmacytomas may express cell surface immunoglobulin idiotypic antigens, these are not the major surface antigens that act as tumor‐associated antigens.