Characterization of a subpopulation in neonatal thymus which suppress the graft-vs.-host reaction

Thymus cells from neonatal and infant mice were found to have a high capacity to prevent mortality from acute graft-vs.-host disease as compared with spleen cells from stable radiation chimeras. This suppressive capacity of thymocytes decreases with age after birth as was demonstrated by semi-quantitative cell titrations. This suppressor activity is restricted to syngeneity of the graft-vs.-host disease-including cells. The thymic suppressor cells are Thy-1+ and Lyt-1+ and IgG- and IgM-. They do not agglutinate with peanut agglutinin and have a high electrophoretic mobility. In vitro irradiation experiments showed that the suppressor cells are radiation sensitive. These results are compared with the available information on cells suppressing delayed-type hypersensitivity reactions and those suppressing B cell responses.