PD-L2在小鼠未成熟树突状细胞上的表达及其生物学意义

Expressions of PD-L2 in Mouse Myeloid Dendritic Cells and Its Role in Activation of T Lymphocytes

目的探讨PD-L2分子在小鼠未成熟DCs上的表达及其在T细胞活化中的作用。方法采用GM-CSF和IL-4联合方案体外诱导小鼠髓系DCs,采用FITC-Dextran吞噬实验和3H-TdR掺入试验鉴定未成熟DCs;采用流式细胞术检测未成熟DCs和经抗原负载及TNF-α刺激成熟的DCs上PD-L2、CD80和CD86的表达;混合淋巴细胞反应(MLR)和抗PD-L2单抗阻断试验分析未成熟DCs表达的PD-L2分子对T淋巴细胞的共刺激效应;3H-TdR掺入试验检测未成熟DCs对T淋巴细胞的促增殖效应;ELISA测定各组MLR反应上清中IL-2的分泌水平。结果经GM-CSF和IL-4联合方案体外诱导5～6d天的DCs抗原吞噬能力最强,且CD80和CD86的表达为中等水平,刺激T细胞增殖能力较TNF-α作用48h的DCs显著低下,其可视为未成熟DCs,未成熟和成熟DCs均表达PD-L2分子,但未成熟DCs的表达较为低下,且未成熟DCs表面PD-L2分子可抑制T细胞的增殖,抑制T细胞分泌IL-2。结论PD-L2分子表达在未成熟DCs可通过下调T细胞分泌IL-2介导未成熟DCs免疫不应答效应。

Objective To study the role of PD-L2 on the surface ofmurine immature DCs in mediating T cell activation.Methods Immature DCs （imDCs） were characterized by FITC-Dextran assay and 3H-TdR incorporation test. Expressions of PD-L2 on imDCs and TNF-α matured dendritic cells （mDC） were analyzed by FCM. ^3Hthymidine incorporation test was used to detect the T cell proliferation stimulated by imDCs with or without blocking PD-L2 by mAb,respectively. The concentrations of IL-2 in supernatants of MLR from distinct groups were analyzed by ELISA.Results 5-6th day DCs in our system can be regarded as imDCs.PD-L2 was expressed on KLH priming-DCs,and could be markedly up-regulated by TNF-α .Blockade of PD-L2 on imDC promotes T cell proliferation and enhances IL-2 secretion. Conclusion Expression of PD-L2 on imDC might contribute to its immunoinhibitory effect,perhaps though down-regulating IL-2 production.