RECRUITMENT OF HELPER T-CELLS FOR INDUCTION OF TUMOR REJECTION BY CYTOLYTIC T-LYMPHOCYTES

Immunotherapy of cancer could be possible in cases in which competent effector T cells can be induced. Such an approach depends on expressio n of tumour-specific antigens by the tumour cells and on the availabil ity of sufficient costimulatory support for activation of cytotoxic T lymphocytes. Here, a strategy for helper T cell recruitment for induct ion of tumour-specific cytotoxic immune responses is presented. Alloge nic MHC class II molecules were introduced into tumour cells by cell f usion. These hybrid cells, when injected into mice, induced rejection of an established tumour. The contribution of CD4-expressing helper T cells in the induction phase and of CD8-expressing T cells in the effe ctor phase of the immune response was demonstrated. The approach descr ibed could be applicable to cases in which a suitable tumour antigen i s present but not identified; it employs regulatory interactions that govern physiological immune responses and is designed to be minimally invasive.