Tfh cells: linking the gut microbiota to a gut-distal autoimmune disease

描述（由申请人提供）：肠道微生物群与肠道内外（肠道远端/全身）的许多自身免疫性疾病有关。然而，肠道中的细菌如何影响肠道远端疾病仍然是未知的。显著 从研究几种特定的细菌（包括分节丝状细菌（SFB））和宿主的相互作用中已经获得了一些见解。这些细胞可以影响某些T细胞亚型，包括辅助性T细胞1（Th 1），Th 17和调节性T细胞（Tcl 4）。然而，几乎没有什么是已知的如何或哪些激素影响T滤泡辅助细胞（Tfh）。Tfh细胞是一种重要的T细胞类型，其帮助B细胞在生发中心（GC）产生高亲和力抗体（Abs）。然而，过度活跃的Tfh细胞应答可导致自身免疫。我们已经建立了一个新的和更生理相关的平台，通过将SFB引入无特异性病原体（SPF）（而不是无菌，我们的旧方法）K/BxN自身免疫性关节炎小鼠来研究免疫效应，其疾病机制依赖于Tfh细胞和自身抗体。与GF小鼠一样，SFB强烈增强SPF K/BxN小鼠的疾病和自身抗体产生。值得注意的是，我们的初步数据表明SFB在Tfh细胞中的作用，因为与SFB（-）K/BxN小鼠相比，在SFB（+）中观察到Tfh和GC细胞群的增加。据我们所知，这是第一个显示特定共生类型与Tfh细胞相关的数据。因此，我们假设肠道微生物群可以通过增强Tfh细胞反应来驱动肠道远端自身免疫性疾病。我们将：1）评估系统性Tfh细胞的SFB依赖性扩增的机制; 2）测试SFB是否通过诱导Tfh细胞细胞因子或将其他Th亚型重编程为Tfh细胞来增加自身Ab产生;和3）评估肠道是否可以充当Tfh引发位点，这是系统性（脾）Tfh细胞应答所需的。我们将确定SFB是否通过增强增殖、存活和/或分化来增加Tfh细胞。我们将使用逆转录病毒系统来观察 SFB依赖性细胞因子的过表达可纠正SFB（-）K/BxN Tfh细胞中自身抗体诱导的缺陷。我们还将测试SFB是否通过增加Tfh细胞通过其他Th亚型（体外偏斜或离体分离）的重编程来增强自身抗体的产生。我们的新数据显示，肠道派伊尔集合淋巴结（PP）中Tfh细胞的巨大SFB依赖性增加。我们期望看到PP Tfh反应比脾Tfh反应更早发生，这表明肠道而不是脾是Tfh引发位点。我们将通过产生肠淋巴组织缺陷的K/BxN小鼠来检查肠Tfh细胞在脾Tfh反应中的作用。我们预计，SFB将不再增强K/BxN小鼠与肠道Tfh缺陷的脾Tfh反应。研究对Tfh细胞的生物效应将对公共卫生产生至关重要的影响，因为现代医学实践引起的生态失调可能会通过影响Tfh细胞引发自身免疫。这将有助于我们了解自身免疫的发病机制，并为新的治疗方法提供新的基础。

DESCRIPTION (provided by applicant): The gut microbiota has been implicated in many autoimmune diseases, both inside and outside the gut (gut- distal/systemic). However, how bacteria that reside in the gut affect the gut-distal diseases remains largely unknown. Significant insights have been gained from studying the interactions of several specific commensals, including segmented filamentous bacteria (SFB), and the host. These commensals can affect certain T cell subtype(s) including T helper 1 (Th1), Th17, and regulatory T cells (Tregs). However, almost nothing is known about how or which commensals impact T follicular helper (Tfh) cells. Tfh cells are a crucial T cell type that helps B cells produce high-affinity antibodie (Abs) in the germinal center (GC). However, an overactive Tfh cell response can lead to autoimmunity. We have established a new and more physiologically relevant platform to study the commensal effect by introducing SFB into specific-pathogen-free (SPF) (rather than germ-free, our old approach) K/BxN autoimmune arthritis mice, whose disease mechanism relies on Tfh cells and auto-Abs. As in GF mice, SFB strongly enhances disease and auto-Ab production in SPF K/BxN mice. Notably, our preliminary data indicate a role for SFB in Tfh cells, as an increase in the Tfh and GC cell populations was observed in SFB (+) compared to SFB (-) K/BxN mice. To our knowledge, this is the first data showing an association of a specific commensal type to Tfh cells. Therefore, we hypothesize that gut microbiota can drive gut-distal autoimmune disease by enhancing the Tfh cell response. We will: 1) assess the mechanism for SFB- dependent expansion of systemic Tfh cells; 2) test whether SFB increases auto-Ab production by inducing Tfh cell cytokines or reprogramming other Th subtypes into Tfh cells; and 3) assess whether the gut can serve as a Tfh priming site, which is required for the systemic (splenic) Tfh cell response. We will determine whether SFB increases Tfh cells by enhancing proliferation, survival, and/or differentiation. We will use retroviral systems to see if overexpression of SFB-dependent cytokines can correct the defects of auto-Ab induction in SFB (-) K/BxN Tfh cells. We will also test whether SFB enhances auto-Ab production by increasing Tfh cells through reprogramming of other Th subtypes (in vitro skewed or ex-vivo isolated). Our new data show a tremendous SFB-dependent increase in Tfh cells in the gut Peyer's patch (PP). We expect to see the PP Tfh response occur earlier than the splenic Tfh response, suggesting that the gut, rather than the spleen, is the Tfh priming site. We will examine the role of gut Tfh cells in the splenic Tfh response by generating K/BxN mice that are gut-lymphoid-tissue deficient. We anticipate that SFB will no longer enhance the splenic Tfh response in K/BxN mice with a gut Tfh deficiency. Studying the commensal effect on Tfh cells will have crucial impacts on public health, as dysbiosis caused by modern medical practice might trigger autoimmunity by affecting Tfh cells. This proposal will help us understand the pathogenesis of autoimmunity and provide new foundations for novel therapies.!