Inhibition of T-cell differentiation by an antibody to a soluble thymic factor.

An antiserum to chicken soluble thymic factor (STF) was prepared in rabbits and absorbed with chicken thymocytes until it reacted only with thymic reticuloepithelial cells. When injected into 6-day-old embryonated eggs, this antiserum caused a severe depletion of small lymphocytes in the cortical region of the thymus which was filled with large undifferentiated cells. In addition, reticuloepithelial cells displayed a marked disruption of cytoplasmic elements. The percentage of thymic lymphocytes bearing the T antigen was greatly reduced. It is believed that a factor responsible for differentiation of stem cells into T cells has been inhibited.