Further histological observations on popliteal lymph nodes after interruption of the afferent lymphatic vessels.

Lymphatic vessels afferent to the popliteal nodes in young adult rats and guinea pigs were interrupted at the lowest edge of the popliteal fossa, and regressive changes in the nodes occurring 4 to 16 or 18 weeks after surgery were re-examined histologically. In the rat, some popliteal nodes were drained by lymphatic channel(s) from the tail. After surgery, the popliteal nodes without lymphatic channel(s) from the tail underwent regression of all their constituent deep cortical units and also the peripheral cortex comprising lymph follicles, until at 18 weeks, the lymphoid organization of the node reached a minimal level. On the other hand, in popliteal nodes having a lymphatic channel from the tail, some deep cortical units and the overlying peripheral cortex underwent hypotrophy, leaving the remaining units and their overlying peripheral cortex little affected. In the guinea pig, the treated nodes underwent progressive atrophy and ultimately became rudimentary, or even vanished, after 16 weeks. Treated rudimentary nodes were composed largely of stromal cells only, and these were replaced to a various extent by fat. The present results are discussed in relation to complete and incomplete inhibition of the afferent lymph flowing into the surgically treated nodes.