Bacterial translocation to mesenteric adipose tissue drives pathogenic stromal-B cell interactions leading to inflammatory IgG

项目摘要 抗微生物抗体是克罗恩病（CD）诊断的预测指标， 至5年前诊断，其积累与并发症，往往需要肠道 切除手术在CD患者中，更多的细菌移位至肠系膜脂肪组织（MAT） 与对照相比，一个细菌子集是CD MAT所独有的。与此同时， MAT及其包裹在肠道周围，或称为“蠕动脂肪”，这是受CD影响的组织发炎的标志， 也与并发症有关。抗微生物抗体和蠕动脂肪的病因尚不清楚。 尽管B细胞和基质细胞共同定位在爬行脂肪中与脂肪相关的淋巴簇内，但B和 与健康MAT相比，浆细胞标记是爬行脂肪中上调最高的基因之一， 该组织中的B细胞功能尚不清楚。我们假设微生物易位到MAT促使 脂肪相关淋巴簇中的基质细胞募集B细胞，后者分化为分泌保护性IgM的 浆细胞，抑制细菌抗原的全身传播。持续CD特异性细菌 易位到MAT导致慢性炎症激活基质细胞分泌驱动IgG的细胞因子 类别转换和分化为炎性抗微生物IgG分泌浆细胞。脂肪细胞源性 瘦素在CD患者的MAT中升高，并驱动小鼠结肠炎模型中的炎症。瘦素激活B 细胞，我们发现瘦素进一步驱动优先类别转换为IgG。我们将在无菌环境中解决这一假设。 用分离自CD或健康供体的细菌培养物重组的小鼠，以及在人中 接受肠切除术的CD患者的MAT与肠道炎症相关或无关， 西奈山。在这些模型中，我们将评估哪些细菌易位到MAT，它们如何激活基质， 通过在转录和蛋白质水平上的深入表征，以及它们如何通过 活检培养物中的脂肪细胞（目的1）。接下来，我们将研究CD微生物群对 MAT B细胞及其从保护性IgM到炎性IgG的转变。为此，我们将描述CD微生物群- 驱动B细胞活化、增殖、类别转换和向浆细胞分化的变化。我们还将 确定MAT和基质细胞在体内暴露于CD或健康供体的IgG诱导特性 微生物群最后，我们将研究CD微生物群如何干扰脂肪相关性细胞内的基质-B细胞串扰。 淋巴簇（Aim 2）。通过显示MAT能够产生微生物群特异性B细胞应答， 该提案将粘膜免疫学的研究扩展到粘膜相关脂肪组织。自从爬行 脂肪和抗微生物IgG与CD并发症相关，这些研究有可能揭示 CD病理学的潜在机制，并确定所需的治疗靶点。

Project Summary Anti-microbial antibodies are predictive of Crohn’s disease (CD) diagnosis and are present in patients’ serum up to 5 years before diagnosis, and their accumulation is associated with complications, often requiring bowel resection surgery. In patients with CD, more bacteria translocate to the mesenteric adipose tissue (MAT) compared to controls and a subset of bacteria are exclusive to CD MAT. This coincides with the expansion of the MAT and its wrapping around the intestine, or “creeping fat”, a hallmark of inflamed CD-affected tissue, which also correlates with complications. The etiology of anti-microbial antibodies and creeping fat are unknown. Although B cells and stromal cells co-localize within fat-associated lymphoid clusters in creeping fat, and B and plasma cell signatures are among the most highly upregulated genes in creeping fat compared to healthy MAT, B cell function in this tissue is unknown. We hypothesize that the translocation of microbes to MAT prompts stromal cells in fat-associated lymphoid clusters to recruit B cells, which differentiate into protective IgM-secreting plasma cells, inhibiting systemic dissemination of bacterial antigens. Sustained CD-specific bacterial translocation to the MAT leads to chronic inflammation activating stromal cells to secrete cytokines driving IgG class-switch and differentiation to inflammatory anti-microbial IgG-secreting plasma cells. Adipocyte-derived leptin is elevated in MAT of CD patients and drives inflammation in mouse colitis models. As leptin activates B cells, we posit leptin further drives preferential class-switch to IgG. We will address this hypothesis in germfree mice reconstituted with cultured collections of bacteria isolated from CD or healthy donors, as well as in human MAT associated or not with inflamed intestine from patients with CD undergoing bowel resection surgery at Mount Sinai. In these models, we will evaluate which bacteria translocate to the MAT, how they activate stromal cells by deep characterization at the transcriptional and protein level and how they drive leptin production by adipocytes in biopsy cultures (Aim 1). Next, we will investigate direct and indirect effects of CD microbiota on MAT B cells and their shift from protective IgM to inflammatory IgG. To do so we will characterize CD microbiota- driven changes in B cell activation, proliferation, class-switching and differentiation to plasma cells. We will also determine the IgG-inducing properties of MAT and stromal cells exposed in vivo to CD or healthy donor microbiota. Finally, we will investigate how CD microbiota perturbs stromal-B cell cross-talk within fat-associated lymphoid clusters (Aim 2). By showing that MAT is able to mount microbiota-specific B cell responses, this proposal will expand the study of mucosal immunology to mucosa-associated adipose tissues. Since creeping fat and anti-microbial IgG correlate with complications in CD, these studies have the potential to uncover mechanisms underlying CD pathology and identify needed therapeutic targets.