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

描述(由申请人提供)：肠道微生物区系与许多自身免疫性疾病有关，包括肠道内外(肠道-远端/全身)。然而，肠道微生物区系如何影响肠道末端疾病在很大程度上仍不清楚。值得注意的是，共生关系已被报道影响某些T细胞亚型(S)，包括辅助性T细胞(Th1)、辅助性T细胞(Th17)和调节性T细胞(Treg)，但关于共生性因素如何或哪些影响T滤泡辅助性细胞(TFH)知之甚少。TFH细胞是一种重要的T细胞类型，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细胞反应可能导致自身免疫。我们已经建立了一个新的、更具生理相关性的平台来研究共生效应，方法是将分段丝状细菌(SFB)引入无特定病原体(而不是我们以前的方法)的K/BxN自身免疫性关节炎小鼠，其疾病机制依赖于Tfh细胞和自身抗体。我们的新数据显示，SFB强烈增强了K/BxN小鼠的疾病，并表明SFB在Tfh细胞中发挥了作用，因为与SFB(-)K/BxN小鼠相比，SFB(+)小鼠的Tfh和GC细胞数量增加。据我们所知，这是第一个将特定共生类型与TFH细胞联系起来的数据。因此，我们假设肠道微生物区系可以通过增强TFH细胞的反应来驱动肠道末端的自身免疫性疾病。我们将研究：1)依赖SFB的全身(脾)Tfh细胞扩张的机制及其在扩大疾病中的意义；2)SFB是否通过诱导Tfh细胞因子、将其他Th亚型重新编程为Tfh细胞或直接作用于B细胞来增强自身抗体反应；以及3)肠道是否可以作为全身Tfh细胞反应所必需的Tfh启动部位。具体地说，我们将讨论SFB是否通过促进增殖、存活和/或分化来增加TFH细胞的数量。我们将通过对CXCR5-/-KRN T细胞使用K/BxN转移模型来确定Tfh细胞是否在SFB介导的疾病中起关键作用，CXCR5-/-KRN T细胞在安装Tfh反应方面存在缺陷。我们将使用逆转录病毒系统来观察过度表达依赖于SFB的细胞因子是否可以纠正SFB(-)TFH细胞的缺陷。我们将通过过继转移体外分离的Th17或Th2细胞来测试SFB是否能将Th17和Th2细胞重新编程为Tfh细胞。我们将使用先天信号缺陷MyD88-/-B细胞的转移模型来测试 SFB可以通过先天受体直接作用于B细胞，从而帮助B细胞。我们的新数据显示，肠道Peyer氏斑(PP)中TFH细胞的数量显著增加，这是SFB的依赖。因此，我们将通过建立缺乏T细胞的小鼠来研究肠道T细胞在脾Tfh反应中的作用。 肠淋巴组织(使用整合素？7-/-KRN T细胞转移模型)。重要的是，我们的最新数据表明这一建议具有很强的意义和广泛的应用，因为在K/BxN模型中发现的SFB对Tfh/GC的促进作用也可以在自然和自发的狼疮模型NZB/NZW F1小鼠中得到证实。研究TFH细胞的共生效应将对公众健康产生至关重要的影响，因为现代医学实践导致的生物失调可能会通过影响TFH细胞来触发自身免疫。

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 gut microbiota affects gut-distal diseases remains largely unknown. Notably, commensals have been reported to affect certain T cell subtype(s) including T helper 1 (Th1), Th17, and regulatory T cells (Tregs), but little 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 segmented filamentous bacteria (SFB) into specific-pathogen-free (rather than germ-free, our old approach) K/BxN autoimmune arthritis mice, whose disease mechanism relies on Tfh cells and auto-Abs. Our new data show that SFB strongly enhances disease in K/BxN mice and 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 to associate a specific commensal type with Tfh cells. Therefore, we hypothesize that gut microbiota can drive gut-distal autoimmune disease by enhancing the Tfh cell response. We will examine: 1) the mechanism for SFB-dependent expansion of systemic (splenic) Tfh cells and their significance in augmenting disease; 2) whether SFB boosts auto-Ab response by inducing Tfh cell cytokines, reprogramming other Th subtypes into Tfh cells, or directly acting on B cells; and 3) whether the gut can serve as a Tfh priming site, which is required for the systemic Tfh cell response. Specifically, we will address if SFB increases the number of Tfh cells by enhancing proliferation, survival, and/or differentiation. We will determine if Tfh cells are critical for SFB-mediated disease by using a K/BxN transfer model with CXCR5-/-KRN T cells, which are defective in mounting a Tfh response. We will use retroviral systems to see if overexpression of SFB- dependent cytokines can correct the defects in SFB (-) Tfh cells. We will test whether SFB can reprogram Th17 and Th2 cells into Tfh cells by adoptively transferring ex-vivo isolated Th17 or Th2 cells. We will use a transfer model with innate signaling-deficient MyD88-/- B cells to test if SFB can help B cells by acting directly on them through innate receptors. Our new data show a tremendous SFB-dependent increase in Tfh cells in the gut Peyer's patch (PP). Thus, we will examine the role of gut T cells in the splenic Tfh response by generating mice that lack T cells in gut-lymphoid-tissue (using transfer model with integrin ¿7-/-KRN T cells). Importantly, our latest data indicate strong significance and broad applications of this proposal, as the Tfh/GC enhancing effect of SFB found in the K/BxN model can also be demonstrated in NZB/NZW F1 mice, a natural and spontaneous lupus model. 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.