Accessory cell function in tumor-bearing mice and effects of Corynebacterium parvum

Primary in vivo production of antibody to sheep red blood cells (SRBC) was consistently suppressed in EL 4 tumor-bearing C57BL/6 mice, but the secondary response was not suppressed. This suppressed primary in vivo production of antibody was partially restored by systemic administration of Corynebacterium parvum. For investigation of the mechanism of the immunosuppression in tumor-bearing mice and the effects of C. parvum, the accessory cell function of adherent cells from tumor-bearing mice and C. parvum-treated tumor-bearing mice in in vitro cultures was studied. Peritoneal and splenic cells from tumor-bearing mice were less efficient in promoting in vitro production of antibody to SRBC by macrophage-depleted normal nonadherent cells than the adherent cells from normal mice. C. parvum treatment restored the accessory cell function of splenic adherent cells from tumor-bearing mice but not that of peritoneal cells. Furthermore, adherent cells from tumor-bearing mice did not show suppressive activity against the in vitro plaque-forming cell response.