The Effect of Plasmacytomas on the Immune Response of Mice

Abstract The effect of plasmacytomas on the immune response of mice was studied by examining the number of direct and indirect plaque-forming cells in the spleens of tumor-bearing animals and the capacity of spleen cells from tumor-bearing mice to immunologically reconstitute irradiated mice. These studies revealed that plasmacytomas differ in their ability to depress the primary 19S response. A γ1-producing tumor and a non-producing tumor in BALB/c mice and a γG2b-producing tumor in DBA/2 mice severely depressed the primary 19S response in mice bearing these tumors, while a γG2b-producer in BALB/c mice had either no effect or a stimulatory effect on the primary 19S response of its host. The effect of the tumors could not be correlated with the presence or absence of paraprotein production. The primary 7S response was not depressed in plasmacytoma-bearing mice. The secondary antibody response to SRC, whether primed before or after tumor implantation was unaffected in mice bearing these tumors. Spleen cells from tumor-bearing mice whose immunocompetence was depressed were capable of restoring the immune response of lethally irradiated mice. The data suggest that either the immunologically depressed cells can recover their immunocompetence upon transfer to a tumor-free host or a proportion of cells in the tumor-bearing mice retain their immunocompetence and these latter cells are responsible for the immune reconstitution of the irradiated mice.