Immunosuppressive Activity Associated with a Reticulum Cell Sarcoma of Aged Mice1

Aging BC3Fi hybrid mice frequently develop a reticulum cell sarcoma (RCS) causing marked hyper-cellularity of lymphoid tissues and pronounced suppression of humoral immunity. Cells of malignant spleens gave feeble responses in vitro to thymus-dependent and-independent antigens; moreover, they suppressed normal spleen cell responses to the antigens. The RCS was passed, serially, in young mice and the spleen and ascites cells of these recipients suppressed normal cell responses in vitro. Malignancy re-sulted in a substantial increase in the proportion of spleen cells of relatively lower density as determined by BSA gradient centrifugation; the cells of lower density were strongly immunosuppressive. The suppres-sive cells appeared to be neither typical T cells nor macrophages. Humoral suppressive substances associ-ated with the RCS were demonstrated in vivo. The suppressive influence of the RCS may account for the hostile milieu in old BC3Fi mice with respect to lymphohematopoietic cells. T HE ability of aged individuals to respondto a variety of test antigens is substantially less than that of young adults (Albright &amp