Tumor-induced immunosuppression.

Three tumor systems, including a mastocytoma, plasmacytomas, and a leukemia-lymphoma were studied for their ability to modify humoral immunity to sheep erythrocytes both in vivo and in vitro. All tumors resulted in a depression of the hemolytic antibody plaque-forming cell response in susceptible mice. These studies indicated that the mechanism(s) of suppression, although not fully defined, were different for each model system investigated.