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，肠道微生物群如何影响肠道远端疾病在很大程度上仍然未知。值得注意的是，已有报道称共生物质会影响某些T细胞亚型，包括辅助性T细胞1 （Th1）、Th17和调节性T细胞（Tregs），但对共生物质如何或哪些影响T滤泡辅助性T细胞（Tfh）知之甚少。Tfh细胞是一种重要的T细胞类型，可以帮助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细胞反应可导致自身免疫。我们通过将分节丝状细菌（SFB）引入无特异性病原体（而不是无细菌，我们的旧方法）的K/BxN自身免疫性关节炎小鼠，建立了一个新的和更生理学相关的平台来研究共生效应，其疾病机制依赖于Tfh细胞和自身抗体。我们的新数据表明，SFB强烈增强K/BxN小鼠的疾病，并表明SFB在Tfh细胞中的作用，因为与SFB (-) K/BxN小鼠相比，SFB（+）中观察到Tfh和GC细胞群的增加。据我们所知，这是第一个将特定的共生类型与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。我们将研究：1)sfb依赖性的全身（脾）Tfh细胞扩增的机制及其在增加疾病中的意义；2) SFB是否通过诱导Tfh细胞因子，将其他Th亚型重编程到Tfh细胞中，或直接作用于B细胞来促进自身抗体反应；3)肠道是否可以作为Tfh启动位点，这是全身Tfh细胞应答所必需的。具体来说，我们将讨论SFB是否通过增强增殖、存活和/或分化来增加Tfh细胞的数量。我们将通过使用含有CXCR5-/- krn T细胞的K/BxN转移模型来确定Tfh细胞是否对sfb介导的疾病至关重要，CXCR5-/- krn T细胞在Tfh应答中存在缺陷。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是否可以纠正SFB (-) Tfh细胞中的缺陷。我们将通过过继性转移离体Th17或Th2细胞来测试SFB是否可以将Th17和Th2细胞重编程为Tfh细胞。我们将使用先天信号缺陷MyD88-/- B细胞的转移模型来验证这一点

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.