An in vitro system was used to study lymphocyte interaction with high-endothelial venules (HEV) in rat lymph nodes. The results show that thoracic duct lymphocytes (TDL) are capable of selective adherence to the endothelium of HEV when overlaid onto glutaraldehyde-fixed sections of lymph nodes. At optimal TDL concentration (30 × 106/ml) and incubation temperature (7°C) binding occurs rapidly and the majority of HEV in each section usually shows adherent lymphocytes, the number attaching to each vessel being proportional to the endothelial area. TDL do not bind to other vascular structures in the node and ordinarily there is little adherence to other cells in the section. The results indicate therefore that TDL have surface membrane structures specific for HEV recognition.

Although TDL adhere to glutaraldehyde-fixed HEV, lymphocytes pretreated with fixative lose their capacity to bind. Also incubation performed at 1°C produces a fairly marked reduction in binding capacity of normal TDL. These observations indicate that endothelium of HEV are passive participants in the in vitro reaction whereas metabolic activity is important on the part of lymphocytes. In addition, when incubation is performed at 24°C, binding is severely reduced and at 37°C few, if any, HEV exhibit adherent TDL. It is suggested that lymphocytes that adhere to HEV are capable of rapid dissociation under physiologic conditions, a property that could facilitate entry of lymphocytes into the lymph node after their interaction with the specialized endothelium in vivo.

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This work was supported by Grant AI 10080 from the National Institutes of Health.

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