Th9/IL-9调控Th17应答抗幽门螺杆菌感染的免疫协同保护作用与应答机制研究

Helicobacter pylori(H. pylori) infection can induce immune response, but bacterium can not be cleaned in stomach tissue. Chronic infection of H. pylori lead to associated gastroenterological disease. Though previous research confirmed that traditional CD4+ T- cell played a role in these responses against H. pylori infection, the complex mechanism of protective responses against H. pylori infection remained unclear up to date. In our previous studies, we investigated responses characteristics of different CD4+ T cells subsets in human and mice with H. pylori infection, and found that the response level of Th9 cell which secreted IL-9 increased in H.pylori-infected individual and mice along with Th17 cell responses. In our further IL-9 knockout mice experiment with H. pylori challenge, amount of H. pylori clone in stomach tissue significantly increased compared with wild-type mice postchallenge. Furthermore, Th17 cell responses obviously decreased after IL-9 gene deletion. Above results showed that Th9/IL-9 may play a synergistic protective role with Th17 cell response against H. pylori infection, but these mechanisms of synergistic responses and immunoregulation to Th17 cell were unclear. In current study, these immunological methods, such as immune enhance, Immunological recovery, antibody blocking test and adoptive immunity test, were used to investigate the synergistic effect of Th9/IL-9 with Th17 responses against H. pylori infection and mechanism of immune regulation to specific Th17 cell response in H. pylori infection in wild-type mice, IL-9-/- knockout mice and Rag1-/- mice model. This research will be helpful to further understand the immunological mechanism of CD4+ T cell responses against H. pylori infection. Otherwise, these mechanism of CD4+ T cell responses will also provide theory support to immunological control of H. pylori infection and development of H. pylori vaccine.

幽门螺杆菌(H.pylori)感染可激发机体免疫反应，但未能有效清除病原，导致相关胃肠疾病发生。现已证明CD4+ T细胞在抗H.pylori感染应答中发挥重要作用，但具体保护作用与机制不清。本课题前期研究发现：H.pylori感染可引起人和小鼠Th9/IL-9应答，并伴随Th17应答升高，而在IL-9敲除后小鼠胃粘膜H.pylori定植量显著增加，Th17应答随之明显降低，结果提示：Th9/IL-9可能调控Th17应答发挥抗H.pylori感染的免疫协同保护作用，但应答机制不清。本课题将以野生型小鼠、IL-9敲除小鼠和Rag1-/-小鼠为模型，采用基因缺失、免疫增强与回复、抗体阻断、免疫过继等技术，探讨Th9/IL-9与Th17应答的协同保护效应和免疫调控的分子机制，将为深入认识CD4+ T细胞抗H.pylori感染的复杂免疫作用机制提供新的解释，为其免疫防治提供理论依据和疫苗设计策略。

CD4+T细胞应答在幽门螺杆菌（Hp）慢性感染中发挥重要作用，其中Th9细胞免疫功能与应答机制尚不清楚。本课题针对Th9/IL-9抗H.pylori感染的免疫保护作用以及与Th17细胞协同保护效应和应答调控机制开展研究。结果显示：IL-9敲除后小鼠胃粘膜H.pylori定植量较野生型小鼠显著增加；敲除小鼠IL-17A水平较野生型小鼠显著下降，而IFN-γ水平明显升高。IL-9免疫回复时，回注组小鼠胃粘膜组织中细菌定植量较PBS对照组显著降低；IL-17A表达量显著上升，IFN-γ水平明显下降。野生型Balb/c小鼠进行IL-9免疫增强后H.pylori定植量较未免疫增强组显著下降，IL-17A水平较有所上升，IFN-γ水平下降明显。Th9 细胞过继免疫可显著减少H.pylori 定植量，在与Th17细胞协同过继免疫后H.pylori定植量显著低于Th9单一过继免疫组，显示出Th9细胞与Th17细胞的协同保护作用。在Th17细胞过继免疫同时进行IL-9免疫增强后小鼠胃粘膜组织细菌定植量较对照组显著降低，IL-17A水平显著升高，IFN-γ水平下降明显，而IL-4，IL-10以及Foxp3+的mRNA表达水平在免疫增强组和对照组之间无明显差异，且未见粘膜炎症程度加剧。IL-9抗体阻断后Th17细胞过继免疫小鼠的胃粘膜组织中H.pylori定植量显著高于未阻断组，表明IL-9抗体阻断后Th9细胞与Th17细胞的协同保护作用明显减弱。此外，IL-9敲除削弱小鼠CD4+CD25- T细胞增殖能力，而对CD4+CD25+ T细胞增殖影响不显著； IL-9敲除可导致小鼠CD4+CD25- T细胞分泌IL-17A水平显著下降，而IFN-γ表达量明显升高，而IL-4及IL-10的表达量变化不明显。上述结果表明Th9细胞可与Th17细胞发挥抗H.pylori感染的协同保护效应，且通过其主要效应因子IL-9作用与Th17细胞，调控Th17细胞效应因子IL-17A表达进而发挥协同增强保护作用，同时，Th9和Th17细胞协同应答适度反向抑制Th1细胞应答，避免过度应答造成严重炎症损伤，但对Treg和Th2细胞应答影响不显著。本研究对CD4+ T细胞在抗H.pylori感染的复杂免疫作用与应答机制提供新的认识和理解。

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