Radiosensitivity of suppressor cells in newborn rats.

The resistance of neonatal rats to sustaining adoptive immune responses against heterologous erythrocytes following the transfter of normal thoracic dust lymphocytes was examined. Irradiation of the neonatal rat at levels as low as 350 rad was found to be effective in overcoming this resistance, although preliminary exposure to antigen could interfere with facilitation of adoptive responses by irradiation. It is suggested that the failure of the neonate to sustain adoptive immune responses is explicable on the basis of an active suppression and, as a corollary, unresponsiveness resulting either from macrophage immaturity or the transfer of maternal antibody is discountered as a likely explanation for the immunological behavior of the newborn rat towards the antigens examined.