Immune response in strain 2 guinea pigs to the syngeneic L2C leukemia

Immunization of strain 2 guinea pigs with 10(7) syngeneic Ia+ L2C leukemia cells in adjuvant leads to L2C tumor protection. After subsequent challenges with L2C tumor cells, the sera and spleens of the protected guinea pigs had detectable anti-L2C reactivity. The L2C antibody reactivity was preferentially associated with the IgG1 isotype fraction and bound equally well to Ia+ or Ia- L2C cells but failed to bind to normal guinea pig lymphoid cells or hepatocarcinoma tumor cells. The binding was inhibited appreciably with F(ab')2 fragments specific for the L2C surface IgM idiotypic determinants. By contrast, the same reagent failed to inhibit the specific cytolysis of L2C tumor cells by T lymphocytes present in the spleens of L2C protected guinea pigs. However, the T cell mediated cytolysis was inhibited to some extent by F(ab')2 fragments specific for the B.1 alloantigen on the L2C tumor cells. These results indicate that the specificity of the L2C T effector cells appears to differ from that of the L2C antibodies and that in the elicitation of a humoral response the IgM idiotypic determinants may function as a tumor-associated antigen.