LYMPHOCYTE TRIGGERING VIA L-SELECTIN LEADS TO ENHANCED GALECTIN-3-MEDIATED BINDING TO DENDRITIC CELLS

For proper immune surveillance, naive lymphocytes are recruited from t he blood into secondary lymphoid organs. L-selectin expressed on lymph ocytes plays an important role in the initial attachment of these cell s to high endothelial venules (HEV) in lymph nodes. Previously, we fou nd that triggering via L-selectin resulted in activation of lymphocyte s, followed by an alteration in their adhesion capacity. This suggeste d that L-selectin triggering might play a role in cell-cell interactio ns after lymph node entry. Here, we identify a novel adhesion mechanis m involving L-selectin-triggered lymphocytes and dendritic cells, and we show that, enhanced binding to dendritic cells is mediated by galec tin-3 and not by integrins. Furthermore, it was shown that L-selectin- triggered T lymphocytes exhibited enhanced proliferation in an allogen eic mixed lymphocyte reaction. It is concluded that, in addition to a role for L-selectin in tethering and rolling on endothelium, triggerin g of the molecule on the lymphocyte surface leads to changes that are pertinent for the function of the cell after passing the HEV. We argue that the described adhesion mechanism plays a role in optimizing the initial interaction between dendritic cells and lymphocytes.