DC-SIGN mediates adhesion and rolling of dendritic cells on primary human umbilical vein endothelial cells through LewisY antigen expressed on ICAM-2

Immature dendritic cells (DCs) are recruited from blood into tissues to patrol for foreign antigens. After antigen uptake and processing, DCs mature and migrate to the secondary lymphoid organs where they initiate immune responses. DC-SIGN is a DC-specific C-type lectin that acts both as a pattern recognition receptor and as an adhesion molecule. As an adhesion molecule, DC-SIGN is able to mediate rolling and adhesion over endothelial cells under shear flow. In this study, we show that the binding partner of DC-SIGN on endothelial cells is the glycan epitope LewisY (LeY), expressed on ICAM-2. The interaction between DC-SIGN on dendritic cells and ICAM-2 on endothelial cells is strictly glycan-specific. ICAM-2 expressed on CHO cells only served as a ligand for DC-SIGN when properly glycosylated, underscoring its function as a scaffolding protein. The expression of LeY in endothelial cells is directed by the enzyme FUT1. Silencing of FUT1 results in a decrease in the rolling and adhesion of immature DCs over endothelial cells. The identification of LeY as the carbohydrate ligand of DC-SIGN in endothelial cells opens new possibilities for the manipulation of DC migration.