[The augmentation of tumor-specific immunity by T-T cell interaction]

The present study establishes a tumor-specific immunotherapy model based on the principle of T-T cell interaction mechanism responsible for augmenting the induction of anti-tumor-specific effector T cells. In this model, high incidence of tumor regression was observed in hosts bearing transplantable or autochthonous tumors when these hosts, in which hapten-reactive helper T cells had been generated, received an injection of haptenic solution into the growing tumor mass. This indicated a role of hapten-reactive helper T cells in regressing the tumor. In consideration clinical application of this tumor-specific immunotherapy model, we have also tried to investigate the use of more appropriate haptenic compounds and have succeeded in synthesizing a noble haptenic compound cross-reactive with BCG, a haptenic muramyl dipeptide (MDP) derivative. The results demonstrated that prepriming of BCG and subsequent immunization with syngeneic tumor cells (mitomycin C-treated) modified with the haptenic MDP derivative resulted in the enhanced induction of tumor-specific immunity. Further investigation is in progress to establish a new tumor-specific immunotherapy model by utilizing this haptenic MDP derivative.