Breg对结核菌特异性IL-22应答的调节作用及其机制研究

Mycobacterium tuberculosis (mtb) infection induces high IL-22 and Th22 cell reponses. IL-22 and Th22 have been demonstrated to enhance the anti-microbial activity of macrophage, indicating that they play an important role in protective immunity. Therefore, illustrating regulatory mechanisms of IL-22 response during mycobacterium tuberculosis infection is important for clinical use of IL-22 for prevention and treatment of tuberculosis. Our previous findings showed that CD19+CD5+CD1d+ B cells (Breg) are increased in patients with tuberculosis. Depletion of Breg resulted in significant increase of mycobacterium tuberculosis antigen-specific IL-22 production by perpheral blood mononuclear cells (PBMC).In addition, purified Breg inhibits mtb-specific IL-22 production by B cell-depleted PBMCs. Moreover, the frequency of Breg in PBMCs is significantly higher in patients with tuberculosis than in healthy control and individuals with latent tuberculosis infection. Thus, these data indicated that Breg inhibition is an important mechanism in regulating antigen-specific IL-22 response in patients with TB. However, it remains to be elucidated how Breg regulate antigen-specific IL-22 response. In this study, we will first investigate the effect of Breg on cell death/apopotosis, cell proliferation, and migration of IL-22-producing cells. Second, we will investigate the role of cell-cell contact, cytokine IL-10/IL-4/TGF-beta in Breg regulation of IL-22 response. Third, we will investigate the effect of Breg on dendritic cells and its potential on regulating IL-22 responses. In doing these, we will define the mechanims underlying the regulation of antigen-specific IL-22 response by breg. Our findings in this study will provide new insight for immunotherapy and vaccine design against tuberculosis targeting IL-22 response.

IL-22及产生IL-22的Th22细胞能显著增强巨噬细胞杀灭结核菌的能力，在结核病免疫保护中起重要作用，阐明IL-22应答的调节机制是靶向IL-22免疫治疗结核病的理论基础。我们的前期研究发现，结核患者显著增多的CD19+CD5+CD1d+ B细胞对结核菌特异性IL-22应答的抑制是一个重要的调节途径，但目前尚不清楚抑制作用的具体机制。本项目拟进一步探讨B细胞对产生IL-22的细胞在细胞增殖、凋亡和迁移功能的调节作用；在此基础上，采用Transwell和特异性抗体阻断试验，明确细胞接触和IL-10/IL-4/TGF-β细胞因子在B细胞免疫抑制中的作用；通过分析B细胞对树突状细胞和CD4+CD25+FoxP3+调节性T细胞（Treg）功能的影响，结合细胞消除试验，明确树突状细胞和Treg在B细胞抑制IL-22应答中的作用和可能机制。从而为靶向IL-22的结核病免疫治疗和预防提供干预靶点。

IL-22在抗结核免疫保护中起重要作用。项目明确了CD19+CD5+CD1d+ B 细胞对结核菌特异性Th22的抑制作用，以及抗结核化疗对CD19+CD5+CD1d+ B 细胞数量的影响及其与结核菌特异性细胞因子应答的关系。消除结核患者外周血单个核细胞（PBMC）中CD19+CD5+CD1d+ B 细胞显著增加结核菌特异性Th22细胞应答，但不影响Th1细胞应答；有效的抗痨治疗可以增加结核菌特异性IL-22的产生，同时减少外周血中CD19+CD5+CD1d+ B 细胞的数量（频率），两者的变化呈现负性相关的关系；并发现抗痨治疗减少CD19+CD5+CD1d+ B 细胞数量可能与CD5+ B细胞表面BAFF-R表达水平下调有关。CD19+CD5+CD1d+ B 细胞的抑制作用不依赖IL-10的产生。本项目首次发现有效的抗痨治疗后CD19+CD5+CD1d+ B 细胞数量减少，其抑制结核特异性IL-22的能力减弱，从而使IL-22的水平得以恢复发挥抗结核效应。