Light microscopic, histochemical and ultrastructural studies of human lymph node paracortical venules.

The light microscopic, histochemical and electron microscopic appearances of human lymph node paracortical high endothelial venules are described, and indicate that the vessels are metabolically active and involved in secretion. A comparison is drawn between these vessels and the majority of lymph node vessels lined by flat endothelium. The evidence suggests that these vessels are identical to similar vessels in the lymph nodes of experimental animals and which are known to be the site of selective migration of lymphocytes into lymph nodes. The correlation between the structural and cytochemical findings and their probable function is discussed.