[Functionally active T-cells and T-lymphocyte precursors in the thymus of newborn mice irradiated in the intrauterine period of development].

Mice were irradiated in dose of 2 Gy in 14 or 17 days of gestation. Irradiation retarded the increase of cell number in developing thymuses but in the day of birth the number of thymocytes was normalized. In normal development SC-1+ cells (T cell precursors) disappeared from the thymus immediately before the birth. After the irradiation they persisted in the newborn thymus. Mitogenic responses of newborn thymocytes on the action of thymic peptides and T cell mitogens were decreased after the fetal irradiation (adult irradiation enhances mitogenic response of thymocytes). The helper activity of thymocytes in humoral immunity was decreased after the fetal irradiation in more degree and helper activity in splenic colony-formation--in less degree than after the adult irradiation. The consequences of the irradiation in 14 and 17 days of gestation were similar.