[Heterogeneity of epithelial cells in the human thymus during early ontogeny (an immunohistochemical study)]

An immunohistochemical study of thymic epithelial cells at an early stage of prenatal development of man (II-III lunar month of pregnancy) was carried out. Serial cryostatic sections were prepared by a standardized method (Takacs, 1987) with monoclonal antibodies against four types of tonofilament-bound keratinic antigens (BH11, BG3, AG3, T2/30). There were phenotypic-heterogeneity, caused by differences in the expression of keratinic antigens, as well as regional peculiarities in inner thymic distribution of various types of keratin-positive epithelial cells. The obtained results are discussed in connection with the possibility of securing specific epithelial microencirclement of thymic lymphocytes during their proliferation and differentiation at early ontogeny.