IL-6/STAT3调控髓系来源抑制性细胞在白癜风黑素细胞缺失中的作用及机制研究

Myeloid derived suppressor cells(MDSCs) are potent suppressive cells and have complicated regulatory effect on effector cells in immune response. However, it has been rarely noticed in vitiligo. In our previous study, we found that the proportion of MDSCs was significantly increased in PBMC of patients with progressive vitiligo compared with healthy controls, which was positive related with IL-17A level in serum. It is reported that IL-6/STAT3 is critical for the expansion and recruitment of MDSCs population and IL-6 was greatly elevated both in serum and skin lesions in vitiligo. Based on these data, we supposed that MDSCs were expanded by IL-6/STAT3 and recruited to skin lesions and may play a role in the progression of vitiligo by ROS production and/or th17 induction. We will further investigate the effect of MDSCs and its subsets in the loss of melanocytes in vitiligo by analyzing clinical blood samples and biopsy from active and stable patients, in vitro coculture of MDSCs and melanocytes/T cells and humannized-mouse model of vitiligo. We will systemically explore immune regulation of MDSCs in the pathological progression of vitiligo and its possible mechanism. The aim of this study is to find out the key molecules in the mechanism underlying melanocyte loss caused by MDSCs in vitiligo, which will be the new targets for clinical therapy.

MDSCs是一种强效免疫抑制细胞，不仅能强力抑制效应性免疫细胞反应，还可复杂调节其分化。迄今MDSCs在白癜风中的作用未见报道。我们发现，进展期白癜风患者外周血中MDSCs比例显著高于正常对照，并与血清中IL-17A水平呈正相关。据报道，IL-6/STAT3是刺激、招募及扩增MDSCs的关键因子。而白癜风患者血清及皮损局部IL-6含量均显著增高。我们推测，外周高水平IL-6经STAT3通路刺激MDSCs扩增，并将其募集至皮损局部，原位产生大量ROS等物质直接作用于黑素细胞，和/或通过对Th17等效应性免疫细胞的调节，间接调控针对黑素细胞的自身免疫反应。本课题拟从临床不同阶段患者外周血和皮损样本入手，进一步通过细胞体外实验以及人源化小鼠动物活体实验，系统深入地探讨IL-6/STAT3对MDSCs的调控作用及MDSCs在黑素细胞损伤中的作用及分子机制，为有效遏制白癜风发展提供新的免疫治疗靶点。

MDSCs是一种强效免疫抑制细胞，不仅能强力抑制效应性免疫细胞反应，还可复杂调节其分化，在多种自身免疫性疾病中发挥重要作用。迄今MDSCs在白癜风中的作用尚未见报道。本课题通过对外周血、临床病理组织以及体外培养等研究发现，与健康对照相比，NSV患者外周血中MDSCs比例显著增高，其中gMDSCs亚群比例增高显著，伴有血清中NO水平显著降低，而NOS、iNOS、TNOS和Arg水平则未见显著变化。患者血清中IL-17A含量显著增高，并且与PBMCs中MDSCs比例呈正相关。体外实验证实，MDSCs可促进Th17细胞分化。白癜风皮损处皮下组织内有大量CD4+T细胞和CD8+T细胞浸润，一部分CD8+T细胞可侵入至表皮基底层。可见较多的IFN-γ+淋巴细胞和IL-17A+细胞，而表达IL-4的淋巴细胞则较少见。另外，我们选用NCG小鼠，构建HLA-A2限制性MART-1特异性TCR转基因人源化小鼠，发现移植人皮肤中人CD45+细胞浸润显著高于小鼠皮肤，其中大部分为CD3+T细胞，少量CD11c+树突状细胞，极少CD19+B细胞浸润。未经局部处理时，人源化小鼠外周血、脾脏等组织检测到不同水平MART-1特异性T细胞表达，它们绝大多数为幼稚型，移植皮肤中未检测到MART-1特异性T细胞；用咪喹莫特或咪喹莫特联合抗原肽连续处理后，移植人皮肤中均有不同水平MART-1特异性T细胞浸润；而且只有皮肤中MART-1特异性T细胞数量最高的2只小鼠的移植皮肤真表皮交界处观察到MART-1+黑素细胞减少现象，但模型仍有待进一步优化。基于以上结果，我们首次提出MDSCs可能通过调节Th17分化参与了白癜风的病理发生。而项目的完成有助于拓展对白癜风发病机制的认识，为临床的免疫治疗提供了新的靶点。