In vitro suppression of immunocompetent cells by lymphomas from aging mice.

We studied the effects of lymphomas in the spleens of aging (C57BL/6 X BALB/c)F1 (B6CF1) mice on the immunologic responsiveness of normal spleen cell cultures to sheep erythrocytes. The cultures were assayed for antibody-forming cells (AFC). Cultures of 20 times 10-6 normal spleen cells produced hundreds of AFC, whereas similar cultures of lymphomatous spleen cells produced less than ten AFC. Normal spleen cells were immunosuppressed in cultures with as few as 10-4 lymphomatous spleen cells. Our results demonstrated that lymphoma cells inhibited the response of normal spleen cells to antigenic stimulation in vitro. The age response for male mice gave a biphasic decline with a steeper second phase. This second decline of immune responsiveness started to appear as the incidence of lymphomas rose. This suggested that the immunosuppressive activity of lymphoma cells was causally related to the age-dependent decline of immune responsiveness in B6CF1 mice.