Immunohistochemical and functional studies on rat high endothelial venules using monoclonal antibodies.

The distribution of high endothelial venules (HEVs) in various rat organs has been investigated immunohistochemically using two monoclonal antibodies (MoAbs), REC16-11 and REC4-1. The staining patterns observed with REC16-11 and REC4-1 were compared with those obtained with the MoAb anti-rat ICAM-1, which is a cell adhesion molecule in HEVs. REC16-11 reacted not only with HEVs but also with all vascular endothelial cells (ECs) in the tissues examined. Electronmicroscopy showed that REC16-11 and REC4-1 reacted with the cell surface antigens of ECs and immunoblot analysis of rat splenic stromal preparations showed that REC4-1 stained 42 kd and 60 kd bands. REC4-1 inhibited the binding of lymphocyte to HEVs in the mucosa-associated lymphoid tissues (MALT), but had no effects on lymphocyte binding to HEVs in peripheral (non-mucosal) lymph nodes. These findings suggested that the MoAb REC4-1 recognized the associated antigen of the lymphocyte-HEV recognition system in MALT.