Analysis of Immune Cell Function in Leprosy Lesions

描述（由申请人提供）：麻风病是一种由细胞内病原体麻风分枝杆菌（mLEP）引起的人类疾病，它为研究对感染的免疫反应提供了一个有吸引力的模型，因为这种疾病代表了一个谱系，其中临床表现与对病原体的免疫反应相关。通过研究麻风病，我们发现了一种新的途径，涉及nod2介导的IL-32诱导，触发单核细胞向CD1+ DC分化，具有专业抗原递呈细胞功能。尽管IL-32或GM-CSF衍生的DC均能通过MHC II类有效地摄取、加工和呈递外源抗原到CD4+ T细胞，但只有IL-32衍生的DC通过MHC I类“交叉呈递”外源抗原到CD8+ T细胞。通常，MHC I类在细胞质中采集抗原，这在专业抗原呈递细胞中导致幼稚的CD8+ T细胞活化，成为细胞毒性细胞，这是宿主防御感染所必需的。因此，当抗原位于抗原呈递细胞的内吞途径时，即当病原体位于内吞途径或抗原是外源性获得时，诱导CD8+细胞毒性T细胞反应需要“交叉呈递”。我们假设CD8+ T细胞识别mLEP抗原是由于IL-32诱导的交叉呈递，从而引发麻风病的抗菌反应。我们建议：1)阐明IL-32诱导mLEP抗原向CD8+ T细胞交叉呈递的机制；2)确定CD8+ T细胞识别mLEP感染的单核/巨噬细胞的抗原呈递机制，包括维生素D抗菌途径在交叉呈递中的作用；3)了解MHC i类限制性CD8+ T细胞参与麻风病宿主防御的机制。我们提出的研究旨在对CD8+ T细胞的交叉呈递和诱导进行全面分析，以深入了解宿主对内吞途径中微生物病原体的防御机制。我们希望获得的见解将确定诊断的新生物标志物，以及治疗慢性人类传染病的靶点。

DESCRIPTION (provided by applicant): Leprosy, a human disease caused by the intracellular pathogen Mycobacterium leprae (mLEP), offers an attractive model for investigating immune responses to infection as the disease represents a spectrum, in which the clinical manifestations correlate with the immune response to the pathogen. By investigating leprosy, we discovered a novel pathway involving NOD2-mediated induction of IL-32, triggering the differentiation of monocytes into CD1+ DC with professional antigen presenting cell function. Although either IL-32 or GM-CSF derived DC efficiently take up, process and present exogenous antigen via MHC class II to CD4+ T cells, only IL-32 derived DC "cross-present" exogenous antigen via MHC class I to CD8+ T cells. Typically, MHC class I samples antigen in the cytoplasm, which in professional antigen presenting cells leads to activation of na�ve CD8+ T cells to become cytotoxic cells, required for host defense against infection. Therefore, "cross- presentation" is required to induce CD8+ cytotoxic T cell responses when antigen is located in the endocytic pathway of antigen presenting cells, i.e. when a pathogen resides in the endocytic pathway or antigen is acquired exogenously. We hypothesize that CD8+ T cells recognize mLEP antigens as a result of IL-32 induced cross-presentation, triggering an antimicrobial response in leprosy. We propose to: 1) elucidate the mechanism(s) by which IL-32 induces cross-presentation of mLEP antigen to CD8+ T cells; 2) determine the mechanism of antigen presentation by which CD8+ T cells recognize mLEP infected monocytes/macrophages including the role of the vitamin D antimicrobial pathway in cross-presentation; and, 3) understand the mechanisms by which MHC class I-restricted CD8+ T cells contribute to host defense in leprosy. The studies we propose are intended to provide a comprehensive analysis of cross-presentation and induction of CD8+ T cells to gain insight into mechanisms of host defense against microbial pathogens that reside in the endocytic pathway. We would hope that the insights gained will identify new biomarkers for diagnosis, as well as targets for treatment of chronic human infectious diseases.