Cortical structure of the lymph node. I. Effect of blockage of the afferent lymph flow to mouse popliteal nodes for protracted periods.

Changes in the lymphoid organization of the popliteal lymph nodes in mice, under conditions where the afferent lymph flow to the nodes was kept blocked for a protracted period, were the subject of this study. Surgical operations to interrupt the afferent lymphatics of the popliteal nodes were performed and the afferent lymph flow remained blocked for 15 weeks after the operation. A striking accumulation of small lymphocytes occurred within the nodes and the cellular density of the parenchyma and lumina of the sinuses greatly increased. These changes persisted throughout the 15 weeks period of observation. Germinal centres gradually diminished in size and ultimately disappeared completely from most of the operated nodes. Lymphatic nodules, which were aggregations of B lymphocytes, decreased in size to some extent but the number of these structures per whole node was not significantly different from that of the unoperated node. The deep cortex remained highly populated with small lymphocytes and showed no indication of fading out or of being replaced by the medullary structures.