['Dendritic cells (DCs) are the principal antigen-presenting cells involved in primary immune response and immunoregulation. The function of DCs is believed to depend on their degree of maturation. Mature DCs activate immune responses, whereas immature DCs (imDCs) tend to induce immune tolerance. CD1 is involved in regulating the development of imDCs, which have important roles in initiating or suppressing the immune response after transplantation.', 'We used male BALB/c mice and C57BL/6 mice (aged 8-10 wk, 18-22\xa0g). We isolated and purified T lymphocytes from mouse spleen. Immature DCs modified by viral delivery of interleukin-10 (IL-10) were stimulated with granulocyte macrophage colony-stimulating factor and lipopolysaccharide (LPS) and treated with anti-CD1d in\xa0vitro. We used mixed lymphocyte cultures to evaluate the heterogeneity of T lymphocyte response. We also examined the proliferation of T lymphocytes and the expression of cytokines.', 'CD1d blockade did not impair granulocyte macrophage colony-stimulating factor and LPS-stimulated DC maturation. We observed a dramatic increase in allogeneic T lymphocyte proliferation (stimulation index) at all tested responder-stimulator ratios in response to imDCs cultured in the presence of LPS (P\xa0<\xa00.05). CD1d has an important role in imDC-primed T\xa0cell response (P\xa0<\xa00.05). CD1d blockade reduced the capacity of imDCs to prime allogeneic T\xa0cells. T cells pre-sensitized by LPS-stimulated imDCs showed remarkably elevated proliferation in response to T cells from either BALB/c or C57BL/6 mice (P\xa0<\xa00.01). We observed a significant decrease in the proliferation of T cells pre-sensitized by stimulated imDCs after CD1d blockade. Lipopolysaccharide stimulation caused elevated the production of IL-12 and tumor necrosis factor-α (TNF-α) (P\xa0<\xa00.01) and decreased the secretion of IL-10 (P\xa0<\xa00.05). The addition of CD1d neutralization antibody did not significantly change the concentrations of IL-12, TNF-α, or IL-10 produced by imDCs cultured in the presence of LPS (P\xa0>\xa00.05).'] Does cD1d blockade suppress the capacity of immature dendritic cells to prime allogeneic T cell response?