High endothelial-like venules in chronically inflamed periodontal tissues exchange polymorphs

A survey of 58 gingival biopsies revealed the presence of periodontal high endothelial-like venules (PHELVs) in chronically inflamed gingival tissues. PHELVs were found to exchange polymorphonuclear cells (PMNs) almost exclusively in advanced periodontitis, with PMNs greatly exceeding the number of mononuclear cells found in PHELVs (P less than 0.001). Electron microscopy confirmed the emigration of PMNs from these vessels. The enzyme histochemical and ultrastructural features as well as the 35SO4 uptake properties of PHELVs were similar to those of the well-characterized high endothelial venules (HEVs) of rat lymph nodes. It is generally accepted that HEVs in lymphoid tissues and inflammatory sites are specially adapted to assist in the emigration of lymphocytes. However, the observation of preferential PMN emigration in the apparent absence of lymphocyte exchange from PHELVs compels further investigation of other possible functions for HEVs. In relation to this, endothelial cells are capable of producing potent cytokines and inflammatory mediators which may contribute to the development of lesions, and the possibility is discussed that high endothelial cells are functionally adapted to enhance the production of such factors.