Biological capabilities of the thymus of human fetus during normal development and during constant exposure to small doses of radiation after the accident at the Chernobyl power plant

: The literature information and the authors's data are presented on the lability of human fetus thymus changes under extremal conditions. In particular, the source of the thymus development is discussed determining its morphogenetic potencies, the sequences of its endocrine and lymphocytopoietic function appearance. Lymphocytes composition and kinetics of their quantity in the process of fetus development and thymus response to the unfavourable conditions of the mother are presented.