In vitro desensitization of sensitized murine lymphocytes by a serum factor (soluble antigen?)

The possibility that lymphocytes sensitized to cell-associated antigens may be rendered hyporeactive toward cells expressing these antigens by prior incubation with such antigens in soluble form was investigated. Mice were sensitized to the foreign histocompatibility antigens of an allogeneic strain of mice; lymphocytes from such sensitized mice were incubated with serum from normal mice of the sensitizing, sensitized, and F(1) hybrids of the two strains. These lymphocytes were washed and their in vitro activity against preparations of cells of sensitizing strain origin was measured by modifications of a standard assay. Sera from the sensitizing strain, and from F(1) hybrids of the sensitizing and sensitized strains (which would be expected to contain the soluble histocompatibility antigens to which the lymphocytes were sensitized), abrogated the in vitro activity of lymphocytes against target cells of the sensitizing strain, while serum from the sensitized strain did not. Soluble tumor-specific or histocompatibility antigens may be responsible in part for the specific abrogation of sensitized lymphocyte activity by serum from tumorbearing, successfully allografted, allogeneically pregnant, or chimeric animals.