目的　探讨1,25- 二羟维生素D3 [1,25(OH)2D3] 对脐血单个核细胞来源树突状细胞(DCs) 刺激T 细胞增殖能力的影响。方法　无菌条件下采集脐血，体外分离获得脐带血单个核细胞，经重组人粒细胞巨噬细胞集落刺激因子（rhGM-CSF）、重组人白介素-4（rhIL-4）和重组人肿瘤坏死因子-α（rhTNF-α）培养8 d 诱导分化为DCs，予1,25(OH)2D3(10 nmol/L) 干预。流式细胞术检测DCs 表面分子的表达情况，经CD3 磁珠阳性分选后获得T 细胞，并以羧基荧光素二醋酸盐琥珀酰亚胺酯（CFSE）标记，用流式细胞术检测DCs 刺激自体T 细胞增殖的能力和T 淋巴细胞各亚群的增殖情况；ELISA 法检测混合培养上清中细胞因子水平。结果　1,25(OH)2D3 干预组DCs 刺激同种同体CD3+T 细胞增殖率低于对照组(61.6±8.23 对75.21±6.21)，且CD3+CD4+ 和CD3+CD8+T 细胞亚群的增殖率均降低(59.24±10.22 对74.54±6.89，47.06±12.10 对59.97±9.11)，差异均有统计学意义(P 均<0.05)。DCs 与同种同体T 淋巴细胞混合培养后收集上清液检测细胞因子，1,25(OH)2D3 干预组IL-12 和IFN-γ 浓度均低于对照组(78.84±11.8 对99.06±9.07，9.76±2.75对22.45±2.6)，而IL-4 则高于对照组(49.45±2.84 对35.75±1.89)，差异均有统计学意义(P 均<0.05)。结论　1,25(OH)2D3可抑制脐血单个核细胞来源DCs 刺激自体CD3+CD4+ 和CD3+CD8+T 淋巴细胞增殖反应，且诱导T 细胞免疫应答呈Th2倾向。

　Objective　To explore the effects of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) on the stimulating ability of cord blood monocytes-derived dendritic cells (DCs) to T cells proliferation. Methods　Umbilical cord blood was collected in aseptic condition. Cord blood monocytes were isolated and cultured for 8 days in the presence of rhGM-CSF, rhIL-4 and rhTNF-α for inducing to differentiate DCs, then intervened by 1,25(OH)2D3 (10 nmol/L). The expressions of differentiation and maturation markers on dendritic cells were determined by flow cytometry. Mixed lymphocyte reaction (MLR) was used and T cells were stained with CFSE to observe the stimulating ability of DCs to T cells proliferation by flow cytometry. Cytokines in the culture medium of MLR were measured by ELISA. Results　1,25(OH)2D3 treated-DCs stimulated less CD3+ T cells to proliferate than control group (61.6±8.23 vs. 75.21±6.21, P<0.01). Moreover, lower proliferation of both CD3+CD4+ and CD3+CD8+ T cells was observed in intervention group (59.24±10.22 vs. 74.54±6.89, P<0.05; 47.06±12.10 vs 59.97±9.11, P<0.05) . The IL-12 and IFN-γ levels in the culture medium of MLR in intervention group were significantly lower than control group (78.84±11.8 vs .99.06±9.07, P<0.05; 9.76±2.75 vs. 22.45±2.6, P<0.05), however, the IL-4 level in intervention group were significantly higher than control group (49.45±2.84 vs. 35.75±1.89, P<0.01). Conclusions　1,25(OH)2D3 inhibits the capability of DCs to activate CD3+CD4+ and CD3+CD8+ T cells, and instructs DCs to induce Th2 bias.