[Susceptibility of leukemias with increased antigenicity to immunological lysis]

Leukaemic sublines obtained following in vivo treatment with antineoplastic drugs present increased antigenic properties and these are transmitted in heredity after suspension of treatment. The pharmaco-altered sublines are rejected by compatible animals with related lymphoma. Susceptibility to humoral and cellular immunological lysis on the part of pharmaco-altered sublines with respect to related lines has been studied. Lymphocytes of C3HC57Bl/10 mise and non-inbred rats immune to histocompatibility antigens of mouse DBA/2 exert the same lysis action towards related cells as towards pharmaco-altered cells. The same susceptibility to lysis on the part of various cell populations was observed with cytotoxic antisera obtained in the same animals. Nor did the immunitary response obtained by inoculating the tumours show any different "fragility" to immunological lysis. Rejection of the pharmaco-altered sublines does not appear to be even partially due to increased fragility with respect to immunitary functions.