Visualization of IL-22 expressing cells during anti-infectious immune responses

白介素22(IL-22)是IL-10家族的一种细胞因子，最初发现是由分化的Th17淋巴细胞产生的。最近，在肠道中发现了一种新的产生IL-22的自然杀伤(NK)样细胞，它们共表达淋巴组织诱导细胞(LTI)的标志，如RoR-γt和NK细胞，如NKp46，但只有低的细胞溶解或干扰素γ产生活性。从功能上讲，IL-22通过诱导上皮细胞产生防御素和再生基因家族蛋白，参与组织修复和宿主对感染的防御。例如，由于抗菌肽的产生减少，IL-22缺乏的小鼠表现出对轮状柠檬酸杆菌和肺炎克雷伯菌感染的敏感性增加。虽然Th17和RoRγt NKp46细胞具有产生IL-22的一般能力，但在体内不同宿主器官感染过程中产生IL-22的实际细胞来源仍不清楚。本研究的目的是通过在小鼠胚胎干细胞中同源重组，在内源性IL-22基因座的终止密码子后插入IRES驱动的YFP荧光盒，从而建立IL-22报告小鼠品系。该小鼠品系将用于显示肺炎克雷伯菌、肺炎衣原体和弓形虫的小鼠肺部感染模型中产生IL-22的细胞。这些实验的发现稍后可以扩展，并分别与使用轮状柠檬酸杆菌和单核细胞增生性李斯特菌的肠道和全身感染模型进行比较。由于IL-22的产生依赖于IL-23的产生，因此将IL-22-YFP报告基因与已有的IL-12/23p40-GFP报告基因结合起来，可以同时监测IL-23的调控细胞和IL-22的效应细胞。综上所述，拟议的项目可以对定义产生IL-22的细胞群体、它们的相互作用伙伴以及它们在抗感染免疫反应中的效应机制做出重大贡献。

Interleukin-22 (IL-22) is a cytokine of the IL-10 family initially found to be produced by differentiated Th17 lymphocytes. Recently, a novel population of IL-22 producing natural killer (NK)-like cells in the gut have been identified which co-express markers of the lymphoid tissue inducer (LTi) cells like RORγt and NK cells like NKp46 but have only low cytolytic or IFNγ production activity. Functionally IL-22 has been implicated in tissue repair and host defense against infections by inducing the production of defensins and regenerating gene family proteins in epithelial cells. IL-22 deficient mice, for instance, show an increased susceptibility for infections with Citrobacter rodentium and Klebsiella pneumoniae due to reduced production of anti-microbial peptides. While the general ability to produce IL-22 was demonstrated for Th17 and RORγt+ NKp46+ cells, the actual cellular source of IL-22 production during the course of an infection in different host organs is still poorly defined in vivo. The aim of the study proposed here is to generate an IL-22 reporter mouse line by inserting an IRES driven YFP fluorescence cassette behind the stop codon of the endogenous IL-22 gene locus by homologous recombination in mouse embryonic stem cells. This mouse line will be used to visualize the IL-22 producing cells in the murine lung infection models of Klebsiella pneumoniae, Chlamydia pneumoniae and Toxoplasma gondii. Findings from these experiments can later be expanded and compared to the intestinal and systemic infection models using Citrobacter rodentium and Listeria monocytogenes, respectively. As IL-22 production is dependent on IL-23 crossing the IL-22-YFP reporter to the already existing IL-12/23p40-GFP reporter mouse line will allow to simultaneously monitor the regulating IL-23 producing cells vs. the effector IL-22 producing ones. In summary the proposed project can contribute significantly to the definition of the IL-22 producing cell populations, their interaction partners, and their effector mechanisms during anti-infectious immune responses.