Lymphocyte recognition of lymph node high endothelium. I. Inhibition of in vitro binding by a component of thoracic duct lymph.

Rat thoracic duct lymphocytes (TDL) adhere selectively to HEV when overlaid onto glutaraldehyde-fixed frozen sections of lymph node. The results presented demonstrate that thoracic duct lymph contains a factor capable of inhibiting this reaction. A crude preparation of inhibitory factor was isolated from cell and chylomicron-free lymph by (NH4)2SO4 precipitation (60 to 80% saturation). Sephacryl S-200 chromatography revealed 4 major peaks. The inhibitory factor was detected in peak I but not in the others. Similarly peak I but not peak II or III inhibited HEV binding of lymphocytes from lymph nodes and spleen. Peak I emerged near aldolase (m.w. 160,000) and was enriched approximately 50-fold compared to the crude preparation. In addition, experiments employing a rabbit peak I antiserum provided evidence that molecules responsible for inhibition were antigenically related to structures present on TDL but not on thymocytes. It is suggested that inhibitory factor possesses an affinity for lymphocyte binding sites of high endothelium and is derived from shed TDL surface components that play a role in adherence to HEV of lymph nodes.