[Histochemical differentiation of lymphatic organs during intrauterine development]

The activities of some enzymes (phosphatases, esterases peptidases, and dehydrogenases) were studied. The activities of the enzymes in the youngest embryos (4-8 weeks) were relatively low (ALP-activity on membranes of the primitive capillary endothelium, ACP and UE activities in the cytoplasm of the epithelial reticulum cells). The DPP IV activity was observed on membranes of the epithelial reticulum cells. The activities of GPDH and SDH were relatively strong in the epithelial cells of the primitive cytoreticulum. In the fetal period, the activities of the studied enzymes are gradually increasing. The immunohistochemical findings demonstrate that 95% of the lymphocytes in the thymus anlage (in the fetal period) are T-lymphocytes. The enzyme activities in other lymphatic organs (spleen, lymph nodes) were significantly lower.