Ly 1+2− suppressor T cells down-regulate the generation of Ly1−2+ 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^-2⁺ T cells which are capable, on passive transfer, of causing the regression of an established tumour in γ-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⁺2^- 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 mastocyroma 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. [ABSTRACT FROM AUTHOR]