CD44 IS NOT DIRECTLY INVOLVED IN THE BINDING OF LYMPHOCYTES TO CULTURED HIGH ENDOTHELIAL-CELLS FROM PERIPHERAL LYMPH-NODES

The Ager assay was adapted to a porcine lymphocyte-rat high endothelia l cell (HEC) system. Using this in vitro assay, the role of porcine CD 44 in lymphocyte binding to HEC was examined. The results show that th e presence of soluble CD44 molecules did not inhibit the binding of po rcine lymphocytes to the cultured rat HEC. Treatment of lymphocytes wi th anti-CD44 monoclonal antibodies (mAb), or with papain, which remove s a 45,000 MW peptide from the intact CD44 molecule, did not inhibit t he binding. Binding to the rat HEC did not induce modulation of CD44 m olecules on the cell surface. Furthermore, modulation of the CD44 mole cule by biotinylated anti-CD44 antibody followed by streptavidin-phyco erythrin, which had caused the molecule to cap on the cell surface, di d not prevent the cells binding to the HEC. Similarly, cells denuded o f CD44 by anti-CD44 antibody retained the capacity to bind to HEC. Mor eover, the binding cells were mainly those which had been stripped of CD44 by the antigenic modulation. It is concluded that CD44 is not dir ectly involved in the binding of lymphocytes to the cultured HEC from peripheral lymph nodes (PLN).