Cysteine Proteases in MHC Class II Antigen Presentation

描述：(由申请人提供)：内体半胱氨酸蛋白酶，组织蛋白S，通过其在降解MHCII相关的伴侣，不变链(II)中的作用，在MHC II依赖的免疫中起关键作用。但对组织蛋白酶S-/-小鼠的研究也揭示了意想不到的发现。组织蛋白酶S缺乏主要影响Th1依赖免疫。在组织蛋白酶S-/-小鼠中，免疫球蛋白E反应和Th2驱动的肺部炎症，虽然依赖半胱氨酸蛋白酶，但是正常的或增加的。事实上，这些小鼠的基础IgE水平和肺中促炎症细胞因子的mRNA水平都升高了。令人惊讶的是，高IgE水平和细胞因子依赖于肥大细胞。这些观察结果表明，额外的蛋白水解酶，或许还有额外的抗原提呈细胞(APC)，对MHCII的功能非常重要，而蛋白酶失调可以扭曲，而不仅仅是阻断MHCII依赖的免疫反应。实验旨在了解蛋白酶如何影响与肺部疾病相关的T和B细胞发育的极化。组织蛋白酶S缺乏的APC中肽负载的机制将被定义。最近产生了缺乏II-降解APC蛋白水解酶组织蛋白酶F的小鼠，并将被用来检验组织蛋白酶F拯救髓系APC中MHC-II类多肽显示的假设，从而有利于Th2极化。选择性的蛋白酶抑制剂将被用来确定人类APC中的一组蛋白酶活性是否是过敏原刺激的T细胞产生Th2细胞因子所必需的。肥大细胞促进APC依赖的免疫球蛋白E产生的机制将通过肥大细胞缺陷小鼠(WSH)与S-/-或细胞因子缺陷小鼠培养的肥大细胞重组来探讨。本应用程序的总体目标是了解T细胞和B细胞免疫反应的蛋白酶依赖极化的分子基础，并了解如何利用这一过程来改善CD4+T细胞驱动的疾病，如自身免疫和哮喘。

DESCRIPTION: (provided by applicant): The endosomal cysteine protease, cathepsin S, has a key role in MHC class II (MHCII)-dependent immunity through its role in degradation of the MHCII-associated chaperone, the invariant chain (Ii). But studies of cathepsin S -/- mice also reveal unexpected findings. Cathepsin S deficiency predominantly affects Thl dependent immunity. IgE responses and Th2-driven pulmonary inflammation, while dependent on cysteine proteases, are normal or increased in cathepsin S -/- mice. Indeed baseline IgE levels and lung mRNA of proinflammatory cytokines in these mice are elevated. Surprisingly, high IgE levels and cytokines are mast cell-dependent. These observations imply additional proteases, and perhaps additional antigen presenting cells (APC), are important to MHCII function and that protease dysregulation can skew, not just block, MHCII-dependent immune responses. Experiments are directed toward understanding how proteases can effect polarization of T and B cell development relevant to lung disease. Mechanisms of peptide loading in cathepsin S-deficient APC will be defined. Mice deficient in the Ii-degrading APC protease cathepsin F have been recently generated and will be used to test the hypothesis that cathepsin F rescues MHC class II peptide display in myeloid APCs, thereby favoring Th2 polarization. Selective protease inhibitors will be used to determine if a set of protease activities in human APC are required for Th2 cytokine production by allergen stimulated T cells. The mechanisms by which mast cells promote APC-dependent IgE production will be explored by reconstitution of mast cell deficient mice (Wsh) with mast cells cultured from S-/- or cytokine deficient mice. The overall goal of this application is to understand the molecular basis for protease dependent polarization of T cell and B cell immune responses and to learn how to exploit this process to ameliorate CD4+ T cell driven disorders such as autoimmunity and asthma.