Antigen-induced changes in the lymphocyte-high endothelial venule interaction

The sequential changes of some morphometric parameters (lymph node weight, high endothelial venule (HEV)-content) after an antigenic challenge (sheep red blood cell; SRBC) and the alterations of HEV-function (HEV-adhesiveness measured with a HEV binding assay) were studied in rat lymph nodes over a period of seven days with daily measurements. Authors suggest that the proper estimation of the HEV-content of a lymph node in a HEV binding assay allows to express the HEV-adhesiveness numerically, and to compare the data obtained by this assay quantitatively. The HEV-adhesiveness is the strongest on day 6 after the antigenic challenge, the early increase in weight on day 2 is attributed to an increased blood flow and the changes in the HEV-content are presumed to reflect a simple dilation of HEVs (on day 2) and later (on days 4 and 5) an increase in the height of high endothelial (HE) cells. A crucial role is ascribed to the altered HEV-adhesiveness in the increase of lymphocyte migration to the challenged lymph nodes.