ABSTRACT
Mice from which a MCA-induced sarcoma has been removed and which are exposed to repeated (every three months) tumoral cell transplants, gradually lose their protection against a certain threshold number of cells. Although the survival period after each transplant is longer than in non-protected animals (those that never received a primary tumor) it is seen that while some of them survive for three months (these are the ones to be re-inoculated with tumoral cells) others die. The proportion of mice which die rises with the number of inoculations received; and among those which die, the proportion of mice without localized tumor or neoplastic dissemination is also progressively higher. We do not know why these mice die at a later and cachectic stage without tumor but in a situation resembling a GVH (graft versus host) reaction. Repeated challenge through re-inoculation induces "bradyphylaxis" (progressively diminishing protection). On histopathological examination intense congestion is found, with haemorrhages in the lungs, liver, spleen and kidneys.
