B-cell-intrinsic MHCII Signaling is a Diversifying Force of Selection on IgA Repertoires and the Gut Microbiota

项目摘要 T细胞依赖性（TD）免疫球蛋白A（伊加）反应调节肠道微生物群的组成。如何 B细胞固有的MHCII信号传导是TD伊加反应发展的核心，影响宿主免疫应答。 微生物群的相互作用是未知的。广泛认为MHCII促进效应淋巴细胞的克隆多样性 人口，但这还没有得到验证。在这里，我们提出的证据支持的论点，B细胞- 内在MHCII信号传导控制GC动力学、伊加库多样性和微生物群组成。 此外，来自我们实验的证据还表明，MHCII的B细胞内源性消融和特异性的B细胞内源性消融都可能导致免疫应答。 MHC基因型与肠道细菌传播增强有关。基于这些 观察和Kubinak博士以前的工作，这个R 01试图解决B细胞内在的假设， MHCII信号是伊加浆细胞库中促进克隆多样性的选择的多样化力量 以及微生物组成的个体性。具体目标#1的目的是定义B细胞内在 MHCII在肠道GC反应中的作用;特别关注其在形成浆细胞库中的作用 多样性将使用“Confetti”小鼠模型来直观地证明MHCII消融对GC B细胞的影响。 肠道中的克隆多样性。IgH测序将用于确定MHCII多态性和MHC 杂合性对肠道中伊加库多样性的影响。scRNA测序将用于确定MHCII 影响粘膜和全身浆细胞库之间克隆多样性的重叠。RAG 1-/-骨髓 (BM)嵌合体将用于定量MHCII对肠源性浆细胞交叉接种到 BM。将使用相互BM嵌合体来确定B细胞-内在缺陷的必要性/充分性。 MHCII在调节肠道细菌传播中的作用具体目标#2的目的是测试微生物群 组合物是MHCII依赖性表型。RAG 1-/-和RAG 1-/-IL 7 R-/- BM嵌合体将用于 确定肠道派伊尔斑在驱动肠道中MHCII介导的伊加选择中的作用。微生物 在无菌GFRAG 1-/- BM嵌合体中的定殖实验将确定B细胞内在MHCII的作用 免疫球蛋白A对肠道细菌的作用。RAG 1-/-过继转移模型将用于确定MHCII是否 表面密度影响IgA介导的对微生物和微生物群组成的靶向。最后，一本小说 无菌MHC同源模型将用于明确定义伊加在驱动个体性中的作用， 微生物群组成。这些研究的结果将阐明MHCII在调节B细胞中的内在作用。 粘膜伊加反应、微生物群组成和宿主健康。这是我们知识中的一个关键空白， 与人类健康密切相关。伊加缺乏症是人类最常见的抗体缺乏症， 与MHCII基因的遗传变异密切相关，并已显示导致与MHCII基因相关的生态失调。 慢性炎症这里概述的实验是第一个解决MHC基因型如何影响 肠道微生物群组成和细菌泄漏是慢性免疫激活的有力驱动因素。

Project Summary T-cell-dependent (TD) immunoglobulin A (IgA) responses regulate the composition of the gut microbiota. How B-cell-intrinsic MHCII signaling, which is central to the development of TD IgA responses, influences host- microbiota interactions is unknown. MHCII is widely assumed to promote clonal diversity in effector lymphocyte populations, but this has not been tested. Here, we present evidence in support of the argument that B cell- intrinsic MHCII signaling controls GC dynamics, IgA repertoire diversity, and microbiota composition. Additionally, evidence from our experiments also indicate that both B-cell-intrinsic ablation of MHCII and specific MHC genotypes are associated with enhanced bacterial dissemination from the gut. Based on these observations and previous work by Dr. Kubinak, this R01 seeks to address the hypothesis that B-cell-intrinsic MHCII signaling is a diversifying force of selection promoting clonal diversity in IgA plasma cell pools and individuality in microbiota composition. The objective of Specific Aim #1 is to define the B-cell-intrinsic role of MHCII during GC reactions in the gut; specifically focusing on its role in shaping plasma cell repertoire diversity. A 'Confetti' mouse model will be used to visually demonstrate the effect of MHCII ablation on GC B cell clonal diversity in the gut. IgH sequencing will be used to determine the effect of MHCII polymorphisms and MHC heterozygosity on IgA repertoire diversity in the gut. scRNA sequencing will be used to determine how MHCII influences overlap in clonal diversity between mucosal and systemic plasma cell pools. RAG1-/- bone marrow (BM) chimeras will be used to quantify the effect of MHCII on cross-seeding of gut-derived plasma cells into the BM. Reciprocal BM chimeras will be used to determine the necessity/sufficiency of defects in B-cell-intrinsic MHCII in regulating bacterial dissemination from the gut. The objective of Specific Aim #2 is to test that microbiota composition is an MHCII-dependent phenotype. RAG1-/- and RAG1-/-IL7R-/- BM chimeras will be used to determine the role gut peyer's patches play in driving MHCII-mediated IgA selection in the gut. Microbial colonization experiments in germfree GF RAG1-/- BM chimeras will determine the effect of B-cell-intrinsic MHCII on IgA-targeting of commensal bacteria. A RAG1-/- adoptive transfer model will be used to determine if MHCII surface density influences IgA-mediated targeting of commensals and microbiota composition. Finally, a novel germfree MHC congenic model will be used to explicitly define the role IgA plays in driving individuality in microbiota composition. Results from these studies will address the B-cell-intrinsic role of MHCII in regulating mucosal IgA responses, microbiota composition, and host health. This is a critical gap in our knowledge that is highly relevant to human health. IgA deficiency is the most common form of antibody-deficiency in humans, is strongly linked to genetic variation in MHCII genes, and has been shown to result in dysbiosis that is associated with chronic inflammation. Experiments outlined here are the first to address how MHC genotype influences microbiota composition and bacterial leakage from the gut, a potent driver of chronic immune activation.