Ly 1 super(+)2 super(-) suppressor T cells down-regulate the generation of Ly 1 super(-)2 super(+) effector T cells during progressive growth of the P815 mastocytoma

It has been shown that progressive growth of the P815 mastocytoma in its semisyngeneic B6D2 host results, between days 6 and 9 of tumour growth, in the generation of Ly 1 super(-)2 super(+) T cells which are capable, on passive transfer, of causing the regression of an establised tumour in gamma -irradiated recipients, and of T cells which are capable of lysing P815 tumour cells in vitro. After 9 days of tumour growth, these effector T cells are progressively lost; this is associated with the progressive acquisition of Ly 1 super(+)2 super(-) suppressor T cells which are capable of inhibiting the expression of passively transferred immunity against an established tumour in T-cell deficient recipients. The results are consistent with the hypothesis that this P815 mastocytoma grows progressively, in spite of its immunogenicity, because it evokes the generation of suppressor T cells before enough effector T cells are generated to reject it.