Tumor dependency of concanavalin A-induced potentiation of tumor cell immunogenicity

The immunogenicity of concanavalin A (Con A)-treated tumor cells was examined in 4 histologically distinct tumors originated from 3 different strains of mice. In all of these tumors, Con A-treated tumor cells induced stronger tumor-specific immunity than Con A-free tumor cells as determined from the survival of sensitized mice after live tumor cell inoculation. However, Con A-induced potentiation of tumor cell immunogenicity was dependent on 2 experimental factors associated with the tumor cell vaccine preparation. One was the agent used for inhibiting in vivo transplantability of tumor cells and the other was the dose of tumor cell vaccine. In Meth A, Meth 1, and Lewis lung tumors, glutaraldehyde and Con A-treated cells, but not mitomycin C and Con A-treated cells, induced an enhanced immune resistance, whereas in L1210 leukemia, mitomycin C was more beneficial than glutaraldehyde. Higher doses of Con A-treated tumor cells (up to 10(7)) induced stronger immune resistance in Meth A and Meth 1 tumors, as was the case with L1210 tumor, whereas in Lewis lung tumor there existed an optimal vaccine dose. These results indicate a tumor species dependence of pretreatment agents and cell vaccine doses in inducing immune resistance, although Con A potentiated the immunogenicity of all the tumors tested.