Studies on cellular immunity and its serum mediated inhibition in Moloney-virus-induced mouse sarcomas

A colony-inhibition technique was used to demonstrate lymph-node cell (LNC) mediated immune reactions against tumor-specific transplantation antigens of primary, Moloney sarcoma virus induced mouse sarcomas. Lymph-node cells from mice in which Moloney sarcomas had regressed spontaneously (regressors), as well as LNC from mice carrying progressively growing tumors (progressors), induced by virus inoculation at an age of 14 days or older, reduced the plating efficiency of Moloney sarcoma target cells. Serum from mice with progressively growing Moloney sarcomas, but not from mice with spontaneous mammary carcinomas or methylcholanthrene-induced sarcomas, abrogated the inhibitory effect of regressor LNC on Moloney sarcoma cells. Additional evidence for the specificity of the serum effect was obtained in experiments showing that the protective effect of progressor sera could be specifically removed by absorption with Moloney sarcoma cells. Regressor sera gave no protection against target cell inhibition by regressor LNC. It is suggested that progressor sera contain antibodies which mediate an efferent form of immunological enhancement.