Pathology of lymphoid organs in low-birth-weight human fetuses subjected to antigen-induced influences: a morphological and morphometric study.

To evaluate the pathology of lymphoid organs in low-birth-weight (LBW) human fetuses obtained after premature birth, morphological and morphometric features were studied. The ages of fetuses ranged from 22 to 32 weeks and their weights from 400 to 1180 g. In fetuses at 22-23 weeks without antigenic effects, the lymphoid organs were seen to be well developed and their differentiation was similar to that of full-term fetuses. In older unaffected fetuses (up to 32 weeks), a significant increase in size of the lymphoid organs and a rise in the rate of the differentiation of lymphoid cells were observed. Fetuses exposed to antigen-related diseases underwent morphological changes in lymphoid organs presumably as a consequence of the primary fetal immune reaction. These changes were characterized by a high increase in the number of lymphoblasts and partly of macrophages in the spleen and lymph nodes. Reactive centers in spleen follicles and in lymph nodes, and plasmocytes in all the lymphoid organs, were absent. The main reaction to severe antigenic influences was decompensation of the lymphoid organs manifested morphologically by their devastation as a result of a decrease in the number of small lymphocytes and, in severe cases, of lymphoblasts and macrophages. Exposure of fetuses to antigen-related diseases thus appears to cause marked changes in the normal ontogenesis of lymphoid organs.