Dendritic cells(DCs) are professinal antigen-presenting cells with the ability to initiate primary Tcell responses. While it iswell known that inflammatory stimuli induce the functional maturation of immature DCs, whether adhesion molecule selectins regulate DCmaturation is poorly understood. Using anti-P-selectin lectin-EGF domain monoclonal antibody (PsL-EGFmAb) that blocks the adhesionof P-, E-, and L-selectin, we demonstrate herein that selectins play important role in stimulating functional maturation of immature DCs.Immature DCs are generated from human cord blood CD34+hematopoietic stem/progenitor cells that were cultured in the presence of stemcell factor, Fms-like tyrosine-kinase-3 ligand, granulocyte-macrophage colony stimulating factor, and transform growth factor-β1. Whenstimulated with tumor necrosis factor-alpha(TNF-α), immature DCs differentiated into mature DCs, producing increased levels of costim-ulatory molecules and interleukin (IL)-12 and obtaining the ability to potently activate naive Tcells. Interestingly, in contrast to matureDCs derived from TNF-α-induced immature DC cultures without PsL-EGFmAb, immature DCs treated with PsL-EGFmAb for7 days werecompletely blocked their maturation, as evidenced by decreased expression of costimulatory molecules CD80, CD86, and CD83, inhibi-ted production of IL-12, and inability to activate naive Tcellsin vitro. Thus, blockade of selectins using PsL-EGFmAb will prove to bea valuable tool for the study of the molecuar mechanisms of DC maturation, as well as for the prevention and treatment of DC-mediated au-toimmunity. While it iswell known that inflammatory stimuli induce the functional maturation of immature DCs, whether antigen-presenting cells with the ability to mutate DC maturation is poorly understood. selectin lectin-EGF domain monoclonal antibody (PsL-EGFmAb) that blocks the adhesion of P-, E-, and L-selectin, we demonstrate herein that selectins play important role in stimulating functional maturation of immature DCs. blood CD34 + hematopoietic stem / progenitor cells that were cultured in the presence of stemcell factor, Fms-like tyrosine-kinase-3 ligand, granulocyte-macrophage colony stimulating factor, and transform growth factor-β1. Whenstimulated with tumor necrosis factor-alpha TNF-α), immature DCs differentiated into mature DCs, producing increased levels of costim-ulatory molecules and interleukin (IL) -12 and obtaining the ability to potently activate naive Tcells. Interestingly, in contrast to mature DCs derived from TNF-α-induced immature DC cultures without PsL-EGF mAb, for mature days derived from costimulatory molecules CD80, CD86, and CD83, inhibi-ted production of IL-12, and inability to activate naive T cells in vitro. Thus, blockade of selectins using PsL-EGFmAb will prove to bea valuable tool for the study of the mechanism of DC maturation, as well as for the prevention and treatment of DC-mediated au-toimmunity.