Reversal of Immunosuppression Induced by Murine Leukemia Viruses*

Abstract

BALB/c mice infected with Rowson-Parr virus, a lymphatic leukemia virus isolated from the Friend complex, undergo a rapid depression of antibody response. Spleen cells from these mice in culture show a similar deficit in the response to stimulation with sheep red cells and inhibit the reactivity of normal splenocytes. In an attempt to reverse this immunosuppression, near normal responses were obtained in vitro from infected splenocytes by increasing antigen dose, by adding E. coli lipopolysaccharide, or, more effectively, by cocultivating with small numbers of unfractionated or T cell-depleted peritoneal exudate cells (PC), whereas other manipulations proved ineffective. PC did not prevent the inhibition of normal splenocytes by infected spleen cells, but exhibited substantial restorative activity in vivo. In similar experiments, the immunosuppression exerted by the entire Friend complex could be reversed by PC in vitro but not in vivo. These results indicate that a functional deficit of macrophages may be partially responsible for the immunological impairment induced by leukemia viruses and suggest rational approaches to evaluate the relevance of this impairment to oncogenesis.

Macrophage and Lymphocyte Antibody-Dependent Cellular Cytotoxicity in Spontaneous Leukemogenesis of AKR/J Mice

“…The low cytotoxic capacity found in this work was in accord with the accepted idea that there is an impaired macrophage func tion in leukemia [24]. Even in the old preleu kemic stage, when only a few blast cells infil trate the spleen, the peritoneal macrophages from AKR/J mice exhibited a decreased ADCC which could be responsible for the defective immune function induced by tu mor viruses [25].…”