Tumor idiotype vaccines. VIII. Analysis of protective idiotype in sera and hybridomas derived from tumor-bearing mice with long-term survival.

In this study, the contribution of idiotype-positive antitumor antibodies (anti-Id) in protective tumor immunity was investigated. We have previously shown that among various anti-Id generated and typed as the internal-image Ab2 of the tumor-associated antibody (TAA) gp52, only 2F10 antibody induces protective immunity. Increase of the 2F10 idiotope in sera of tumor-bearing mice correlated with long-term survival, while in mice with short survival the circulating 2F10 idiotype decreased. 2F10+ Ig were purified from sera of tumor-bearing mice with long-term survival and the amount of 2F10+ anti-TAA antibodies was determined. Only about 3% of 2F10+ antibodies are 2F10+ anti-TAA+. Hybridomas were generated from a 2F10 high mouse with spontaneous tumor regression. Only 2 out of 52 tumor-specific hybridomas were 2F10+. These results suggest that the protective effect induced by 2F10 vaccination may not be directly mediated by 2F10+ antibodies but indirectly through the stimulation of a 2F10-specific cellular immune response.