Mechanism of inhibition of immunization with irradiated tumour cells by a large dose of Corynebacterium parvum

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Abstract
As reported previously, the resistance to subsequent isogeneic live challenge with a highly immunogenic murine fibrosarcoma, which is normally evoked by prior subcutaneous injection of 10 6 irradiated tumour cells, is completely abrogated if a large dose (1.4 mg) of Corynebacterium parvum (strain CN6134) is mixed with the irradiated cells. New experiments designed to elucidate the mechanism underlying this phenomenon have revealed no evidence of humoral inhibitory factors or of an increase in suppressor T cells following injection of C . parvum and irradiated cells. The results suggest, on the other hand, that the abrogation of immunization is due to the induction of specific immunological tolerance of tumour antigens since it can be largely reversed by adoptive immunization, and are consistent with the hypothesis that in this model tolerance is due to prolonged trapping and eventual destruction in the regional nodes of lymphocytes which have responded to tumour antigen.