Effects of pregnancy and lactation on the peripheral lymphatic tissue in the mouse: qualitative and quantitative morphology.

Abstract

Effects of pregnancy and lactation on the spleen and the mesenteric, iliac, axillary and popliteal lymph nodes in the mouse were morphologically examined by means of qualitative and quantitative methods. During pregnancy the spleen weight increases to reach a peak at 15 days of pregnancy. After parturition the weight decreases gradually until 20 days postpartum when it has returned to almost normal. Both the red and white pulps increase in volume during pregnancy. After parturition, the volume of the white pulp rapidly returns to normal. The volume of the red pulp remains greater in lactating females than in control females. In non-lactating females the red pulp decreases rapidly in volume after parturition. In the spleen, plasma cells increase in number during pregnancy, and often contain Russell bodies. They are accumulated in large numbers particularly in the marginal zone and periarterial area. After parturition plasma cells decrease rapidly in number. The weight of the mesenteric lymph node undergoes a slight but a significant increase during pregnancy, and decreases in both the lactating and non-lactating groups after parturition. During pregnancy the medulla shows an increase in volume, and the medullary cords are filled with numerous plasma cells. At 10--15 days of pregnancy, plasma cells also occur in groups in the paracortex. They decrease rapidly after parturition. During pregnancy plasma cells are also markedly increased in iliac lymph nodes, but not in axillary and popliteal lymph nodes. The findings were discussed particularly in relation to the immune response of the peripheral lymphatic tissue in pregnancy.