THE L-SELECTIN ANTIBODY FMC46 MEDIATES RAPID, TRANSIENT INCREASE IN INTRACELLULAR CALCIUM LN HUMAN PERIPHERAL-BLOOD MONONUCLEAR-CELLS AND DAUDI LYMPHOMA-CELLS

We report the induction of intracellular calcium mobilization [Ca2+](i ) in normal peripheral blood mononuclear cells (PBMC) and Daudi cells following binding with the L-selectin monoclonal antibody FMC46. The [ Ca2+](i) signal was mediated directly by binding of FMC46 without cros s-linking antibodies. Increased [Ca2+](i) was not induced by other L-s electin antibodies tested (TQ1, Leu8, Lam1.3). The increase in [Ca2+]( i) was rapid and was blocked completely by BAPTA, an arrent which chel ates intracellular calcium. The increase in [Ca2+](i) was observed in calcium-containing as well as calcium free medium, suggesting that FMC 46 caused release of Ca2+ from intracellular stores. In both PBMC and Daudi cells, previous signaling via L-selectin still allowed signaling through crosslinking of surface antigen receptor. These data provide evidence for direct alteration of the stale of lymphocytes after ligat ion of a specific L-selectin epitope. L-selectin-mediated signaling do es not desensitize signaling through the antigen-receptor and could th erefore play a role in preactivating lymphocytes during endothelial tr ansmigration into lymphoid tissues. (C) 1995 Academie Press, Inc.