Impact of Microbiota on Alloimmune Responses in Transplantation

项目摘要 针对移植器官的免疫反应的强度，称为同种异体反应，取决于 关于捐赠者和接受者之间的遗传差异程度以及接受者对这些差异的认识， 免疫系统我们从上一个资助周期的研究表明，微生物群，收集 微生物在体内定植，个体之间存在差异，这是一个额外的新因素，可以因果关系 调节对移植器官的同种异体反应的强度和动力学。与供体和宿主遗传学不同， 微生物群可以被治疗性地操纵，从而提供可能的新干预以保护移植物。 并有助于减少对可能导致严重副作用的免疫抑制药物的需求。 我们最初将身体的微生物群作为一个整体来考虑，并证明了微生物的减少 广谱抗生素（Abx）预处理诱导的多样性，或使用无菌 (GF)小鼠，两者都改善了轻微不匹配的皮肤移植存活率。来自对照的粪便微生物组转移（FMT）， 而不是Abx预处理的小鼠，进入GF小鼠足以加速皮肤移植排斥。这表明 微生物群对影响移植物结果的因果关系以及不同粪便微生物的不同影响， 社区. ABX预处理还延迟了完全不匹配的皮肤移植物、轻微不匹配的肺移植物和完全不匹配的肺移植物的排斥反应。 移植物和MHC II类不匹配的心脏移植物，表明全身微生物群会影响 移植和不育的器官。我们进一步表明，一些微生物群落可以占主导地位， 拒绝的保护。这种保护作用与粪便中存在Alistipes属细菌有关。 此外，小肠、肺和皮肤移植的半衰期比心脏和 肾移植，支持移植物中的肾上腺素也可能影响 同种免疫我们最近的初步实验表明，供体皮肤与单个 表皮葡萄球菌（S. epi），在没有宿主的肠定殖的情况下，可以是 足以加速皮肤移植排斥反应这一结果清楚地表明，同种异体移植物内的微生物群 也影响移植结果。值得注意的是，皮肤S.肾上腺素加速皮肤移植排斥反应 与SPF小鼠或FMT进入GF小鼠的全身微生物群如何加速皮肤移植排斥不同。我们 假设受体肠道微生物群影响整个动物的免疫应答的新范例 通过系统性地上调或下调DC，而供体移植物中的微生物群局部地影响效应物， 在受体同种异体反应性T细胞迁移到移植物中时的同种异体反应阶段。结合使用 TCR转基因T细胞和p：MHC多聚体用于追踪在小鼠中的抗宿主和抗供体免疫应答 平行地，以及选择细菌定殖的不同组织在gnotobiotic小鼠，我们将：1。探讨 仅肠道微生物可以影响远端皮肤移植物排斥的机制; 2.定义 仅皮肤移植局部加速皮肤移植排斥反应的机制。

PROJECT SUMMARY The strength of an immune response against a transplanted organ, termed the alloresponse, depends on the extent of genetic differences between the donor and the recipient and their recognition by the recipient’s immune system. Our studies from the previous funding cycle have shown that the microbiota, the collection of microbes that colonize the body and differ between individuals, is an additional novel factor that can causally modulate the intensity and kinetics of the alloresponse to a transplanted organ. Unlike donor and host genetics, the microbiota can be manipulated therapeutically, thus providing possible new interventions to protect the graft and help reduce the need for immunosuppressive drugs that can cause significant side effects. We initially considered the body’s microbiota as a whole and demonstrated that a reduction in microbial diversity induced by broad-spectrum antibiotic (Abx) pre-treatment, or an absence of microbiota using germ-free (GF) mice, both improved minor mismatched skin graft survival. Fecal microbiome transfer (FMT) from control, but not Abx-pre-treated mice, into GF mice was sufficient to accelerate skin graft rejection. This demonstrated both the causality of the microbiota on affecting graft outcome, and the divergent effects of distinct fecal microbial communities. Abx pre-treatment also delayed rejection of fully mismatched skin grafts, minor mismatched lung grafts, and MHC class II-mismatched heart grafts, indicating that whole-body microbiota affects the outcome of both colonized and sterile organs. We further showed that that some microbial communities could be dominantly protective of rejection. This protection was associated with fecal presence of bacteria of the genus Alistipes. In addition, the half-life of small bowel, lung and skin transplants is much shorter than that of heart and kidney grafts, supporting the hypothesis that the commensals in the graft may also be able to influence alloimmunity. Our recent preliminary experiments demonstrate that colonization of donor skin with the single commensal Staphylococcus epidermidis (S. epi), in the absence of intestinal colonization of the host, can be sufficient to accelerate skin graft rejection. This result clearly demonstrates that microbiota within the allograft also impacts graft outcome. Notably, the mechanism by which skin S. epi accelerates skin graft rejection appears different from how whole-body microbiota in SPF mice or FMT into GF mice accelerates skin graft rejection. We hypothesize a novel paradigm that the recipient gut microbiota affects immune responses in the whole animal by systemically modulating DCs up or down, whereas the microbiota in the donor graft locally affects the effector phase of the alloresponse upon migration of recipient alloreative T cells into the graft. Using a combination of TCR transgenic T cells and p:MHC multimers to track anti-commensal and anti-donor immune responses in parallel, as well as select bacterial colonization of distinct tissues in gnotobiotic mice, we will: 1. Investigate the mechanisms by which gut-only microbes can impact skin graft rejection distally; 2. Define the mechanisms by which skin-only commensals locally accelerate skin graft rejection.