Soluble tumor antigen-induced lymphocyte proliferation: Effects of serum from normal and tumor-bearing mice

Abstract

The effect of serum from mice bearing methylcholanthrene‐induced fibrosarcomas on the lymphoproliferative responses of their spleen and lymphnode cells to 3 M KCI‐solubilized tumor antigens has been investigated. Low concentrations of serum (≤2.5%) collected throughout the course of tumor growth were inhibitory. Normal sera collected from age‐matched control mice were often slightly inhibitory, but to a significantly lesser extent at identical serum concentrations. The inhibitory effect of tumor‐bearing serum was not limited to homologous tumors, but was also observed when cross‐reacting syngeneic tumor antigens or serum from animals bearing other syngeneic tumors were added to the assay mixture. At the low concentrations used, tumor‐bearing sera inhibited only tumor‐antigen‐induced proliferation, and not proliferation induced by T cell mitogens. The inhibitory effects of tumor‐bearing sera on lympho‐proliferative responses to soluble tumor antigens appear to be similar to the inhibition seen as “serum blocking” in other assays of tumor immunity.