Coordination of Innate and Adaptive Immunity in Intestinal Barrier Defense

项目摘要 天然免疫和获得性免疫在肠道屏障防御中的协调作用。肠屏障防御 需要先天性和适应性免疫细胞对粘膜上皮的作用。组织驻留和 移动的先天免疫细胞和适应性免疫细胞都有助于肠道中的屏障防御，但这些细胞如何在肠道中发挥作用？ 在病原体威胁的条件下，人口的协调没有得到充分的理解。白细胞介素-22（IL-22） 是IL-10家族的细胞因子，由3型免疫细胞产生，如3型先天淋巴样细胞（ILC 3） 和Th 17途径的细胞，其作用于屏障组织的上皮细胞以防止细胞外基质的侵入， 病原体IL-22如何协调肠屏障功能仍不清楚。像许多免疫 作为参与宿主防御的细胞因子，IL-22在慢性免疫介导的疾病中上调， 似乎在炎症性肠病（IBD）中起保护作用，可能是通过抑制上皮细胞 由失调的T细胞对肠道微生物组成分的反应引起的损伤。然而，亲- IL-22的增殖作用也与结肠上皮细胞的恶性转化有关， 导致结直肠癌（CRC）。我们和其他人已经表明，在感染性结肠炎模型的 enteropathogenic、C.在啮齿类动物中，可以区分IL-22产生的两个阶段： IL-22+先天性免疫细胞占主导的晚期阶段，随后是IL-22+ T细胞占主导的晚期阶段。 虽然先天性和适应性免疫细胞在感染期间都产生IL-22，但它们各自对感染的贡献是不同的。 屏障保护是未知的，IL-22的作用机制的细节也是未知的。在初步研究中， 使用了新型IL-22报告基因/条件性敲除（cKO）小鼠， 通过研究IL-22产生免疫细胞的亚群，我们发现IL-22产生免疫细胞的位置和功能， 细胞在C.啮齿类感染以ILC 3为主的先天性免疫细胞主要位于 在并局限于分离的淋巴滤泡，它们释放的IL-22被IL-23激活， 在细菌定植的初始位点激活表面结肠上皮细胞。然而，值得注意的是，ILC 3 以保护肠道隐窝，这是由细菌入侵的小鼠与IL-22缺陷针对T细胞。 因此，产生IL-22的T细胞对于通过其激活肠隐窝来保护肠隐窝是必不可少的。 衬里上皮此外，我们还发现了结肠吸收性肠上皮细胞内新的异质性， 发现产生IL-22的T细胞差异性地激活这些群体，以增加脱落和产生 趋化因子的作用。在这个建议中，我们将定义先天和适应性的机制， 免疫细胞对于结肠上皮细胞的不同亚群具有不同的IL-22依赖性作用， 关注IL-22+ T细胞保护结肠隐窝免受细菌侵袭的新功能。这些研究认为， 有望揭示肠道宿主防御中免疫细胞亚群特化的新见解， 在IBD和CRC中控制肠道炎症的机制。

PROJECT SUMMARY Coordination of Innate and Adaptive Immunity in Intestinal Barrier Defense. Intestinal barrier defense requires the actions of both innate and adaptive immune cells on the mucosal epithelium. Tissue-resident and mobile innate and adaptive immune cells each contribute to barrier defense in the intestines, but how these cell populations are coordinated under conditions of pathogen threat are not fully understood. Interleukin-22 (IL-22) is a cytokine of the IL-10 family produced by type 3 immune cells, such as group 3 innate lymphoid cells (ILC3s) and cells of the Th17 pathway that acts on epithelial cells of barrier tissues to prevent invasion of extracellular pathogens. How IL-22 acts to coordinate intestinal barrier function remains undefined. Like many immune cytokines that participate in host defense, IL-22 is upregulated in chronic immune-mediated diseases, and it appears to play a protective role in inflammatory bowel disease (IBD), presumably by restraining epithelial damage caused by dysregulated T cell responses to constituents of the intestinal microbiome. However, pro- proliferative actions of IL-22 have also been implicated in malignant transformation of colonic epithelial cells that leads to colorectal cancer (CRC). We and others have shown that during infectious colitis modeled by the enteropathogen, C. rodentium, there are two phases of IL-22 production that can be distinguished: an early phase dominated by IL-22+ innate immune cells, which is followed by a late phase dominated by IL-22+ T cells. While both innate and adaptive immune cells produce IL-22 during infection, the respective contributions to barrier protection are unknown, as are details of the mechanisms by which IL-22 acts. In preliminary studies that have employed novel IL-22 reporter/conditional knockout (cKO) mice with which to track and/or delete specific subsets of IL-22-producing immune cells, we have found that the locations and functions of IL-22–producing cells are distinct during C. rodentium infection. Innate immune cells, dominated by ILC3s, are primarily located in and restricted to isolated lymphoid follicles, and their release of IL-22 activated by IL-23 acts long-range to activate surface colonic epithelial cells at initial sites of bacterial colonization. Remarkably, however, ILC3s fail to protect the intestinal crypts, which are invaded by bacteria in mice with IL-22 deficiency targeted to T cells. Thus, IL-22–producing T cells are indispensable for protection of the intestinal crypts via their activation of crypt- lining epithelium. Moreover, we have discovered new heterogeneity within colonic absorptive enterocytes and find that IL-22-producing T cells differentially activate these populations for increased shedding and production of neutrophil-recruiting chemokines. In this proposal we will define mechanisms by which innate and adaptive immune cells are specialized for distinct IL-22–dependent actions on different subsets of colonic epithelial cells, focusing on novel functions of IL-22+ T cells to protect colonic crypts from bacterial invasion. These studies hold promise to reveal new insights into specialization of immune cell subsets in intestinal host defense and mechanisms that control intestinal inflammation in IBD and CRC.