[Cellular composition of the mesenteric lymph node cortex in Baikal nerpa during postnatal ontogenesis].

Cellular composition (relative cell content and cell density) of nodules' germinal centers, mantle zones and paracortical zones was evaluated morphometrically in mesenteric lymph nodes of 65 Baikal nerpas (Pusa sibirica Gmelin) aged 1 month-19 years. A significant decrease in the number of large and medium lymphocytes (3 and 1.9 times, respectively) and reticular cells (2.6 times), was found to occur with age, accompanied by an increase in the number of small lymphocytes (1,5 times) and plasma cells (4.9 times). Thus, with age, on one hand, the decline of lymphopoietic function of the lymph nodes was noted, while on the other hand, the intensification of immunocytopoiesis could be observed.