Impact of Microbiota on Alloimmune Responses in Transplantation

项目总结 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 捐赠者和受赠者之间的遗传差异程度及其接受者的认可 免疫系统。我们在前一个资金周期的研究表明，微生物区系，即 在体内定居的微生物在不同的个体之间存在差异，这是另一个新的因素，可以导致 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， 微生物区系可以通过治疗进行操纵，从而提供可能的新干预措施来保护移植物。 并有助于减少对可能导致显著副作用的免疫抑制药物的需求。 我们最初将人体的微生物区系作为一个整体来考虑，并证明了微生物数量的减少 由广谱抗生素(ABX)预处理或使用无菌微生物区系缺失引起的多样性 (GF)小鼠，两者都提高了轻微不匹配皮肤移植物的存活率。来自对照的粪便微生物群转移(FMT)， 但不是ABX预处理的小鼠，转化成GF小鼠足以加速皮肤移植排斥反应。这证明了 微生物区系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预处理也延迟了完全不匹配的皮肤移植、轻微的不匹配的肺移植的排斥反应 移植物和MHC II类不匹配的心脏移植物，表明全身微生物区系影响着 包括殖民器官和无菌器官。我们进一步表明，一些微生物群落可以占主导地位 防止被拒绝。这种保护与泽泻属细菌的粪便存在有关。 此外，小肠、肺和皮肤移植的半衰期比心脏和皮肤移植的半衰期短得多。 肾移植，支持移植物中的共生体可能也能够影响 同种异体豁免。我们最近的初步实验表明，单个供体皮肤的定植 共生性表皮葡萄球菌(S.epi)，在没有宿主肠道定植的情况下，可以 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区系 也会影响移植物的结果。值得注意的是，皮肤S.epi加速皮肤移植排斥反应的机制出现了。 不同于SPF小鼠全身微生物区系或FMT Into GF小鼠如何加速皮肤移植排斥反应。我们 假设受体肠道微生物区系影响整个动物的免疫反应的新范式 通过系统地调节DC向上或向下，而供体移植物中的微生物群局部影响效应器 受者同种异体反应性T细胞向移植物内迁移时的同种异体反应阶段。使用以下组合 TCR转基因T细胞和p：MHC多聚体对小鼠抗共生和抗供体免疫应答的跟踪作用 平行的，以及选择性的细菌在不同组织中的定植，我们将：1.调查 肠道微生物可远端影响皮肤移植排斥的机制；2.定义 仅皮肤共生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.