[Thymocyte differentiation in mouse embryogenesis].

Thymocytes in mouse embryogenesis and their capacity for colony formation in the spleen of irradiated mice were studied by electron microscopy and immunoassay. Thymocytes from 13-day-old mouse embryos were found to have large nuclei with diffuse chromatin and 1-2 nucleoli. The cytoplasm of these cells was found to contain ribosomes, mitochondria and Golgi's complex. These lymphocytes possess colony forming capacity and are not lysed by anti-theta-serum. In 15-day-old mouse embryos, theta-antigen shows on the cell surface, while the number of colonies in irradiated recipient' spleens decreases. In 17-day-old embryos, thymocytes acquire the structure and properties common to mature T cells.