Processing and Presentation of Minor Histocompatibility Antigens that Cause GvHD

次要组织相容性（H）抗原（Ags）在移植物抗宿主（GVHD）的免疫发病机制中起有害作用 即使在HLA相同的骨髓移植的接受者中，也存在GvHD。在本文中，受体次要HAg是 由供体Ag呈递细胞（APC）获得，并由MHC I类分子加工和呈递， 在一个被称为交叉呈递的已被充分研究的过程中，或在一个不太清楚的过程中被II类分子 称为间接呈现。在实体器官移植中，间接呈递需要获得， 受体APC对供体同种异体抗原的加工和呈递。在肿瘤和微生物的情况下 Ag，一种II类+APC-类似于受体细胞-获得驻留在II类阴性细胞中的Ag-类似于 一个供体细胞-并处理和呈递给同源的CD4+（TH）细胞。我们对间接的机械研究 展示揭示了雄性pHY和单核细胞增生李斯特菌衍生的pLLO Ag在被 受体APC进入胞质溶胶。在此，pHY的间接呈递是 免疫蛋白酶体依赖性TAP（细胞溶质至ER肽转运蛋白）和ERAAP（ER相关 氨基肽酶）不依赖的。令人惊讶的是，TAP和ERAAP都转移或破坏了pHY和pLLO， 从而减少它们对TH细胞的呈递。这些发现导致了两个关键问题：（a）类I Ag加工（CAP）机制在全球范围内影响II类限制性Ag呈递;以及（B）细胞溶质如何影响 抗原进入内体/溶酶体进行间接呈递？在试图理解细胞溶质 pHY返回到内/溶酶体中进行呈递，我们排除了宏观自噬作为间接自噬的作用。 HY的呈递在小鼠中进行，其中树突细胞条件性缺乏Atg5。而是 发现同源二聚体TAP样（TAP-L）-一种不同于ER的孤儿内/溶酶体肽转运蛋白- 间接pHY呈递需要常驻TAP 1/TAP 2。根据我们的功能研究，在此， 我们寻求获得间接呈递机制的生物化学见解。因此，我们将测试中央 I类Ag加工机制调节某些胞质Ag库的假说， II类限制性间接呈递。这些抗原在胞质溶胶中被加工，并被转运到胞质内。 TAP-L依赖性机制中的溶酶体。为了验证这一假设，我们将（a）确定CAP是否 机械全面影响H2Ab限制性加工和自我或微生物衍生的胞质 Ags;（B）确定胞质Ags如何进入内体/溶酶体进行间接呈递;和（c）确定 CAP机制是否影响胞质Ag特异性CD4 + T细胞库。成功完成本 这项工作将产生新的生物化学见解，通过II类分子间接Ag呈递。一种机械的 了解II类限制性间接抗原呈递不仅对于开发 本发明不仅可用于规避/治疗GvHD，而且可用于疫苗设计，因为该过程在细胞溶质的呈递中是有效的。 抗原（病毒，细菌，寄生虫）TH细胞，因此，针对肿瘤和病原体的疫苗设计。

Minor histocompatibility (H) antigens (Ags) play a detrimental role in the immuno-pathogenesis of graft-vs-host disease (GvHD) even in recipients of HLA identical bone marrow transplants. Herein, recipient minor H Ags are acquired by donor Ag-presenting cells (APCs) and processed and presented either by MHC class I molecules in a well studied process termed cross-presentation or by class II molecules in a less well understood process called indirect presentation. In a solid organ transplant setting, indirect presentation entails the acquisition, processing and presentation of donor alloantigens by the recipient's APCs. In the case of tumour and microbial Ags, a class II+ APC-likened to a recipient cell-acquires the Ag residing in a class II-negative cell-likened to a donor cell-and processes and presents it to cognate CD4+ (TH) cells. Our mechanistic studies into indirect presentation revealed that the male pHY and Listeria monocytogenes-derived pLLO Ags upon acquisition by the recipient APCs gained access to the cytosol. Herein, the indirect presentation of pHY was immunoproteasome-dependent yet TAP (cytosol to ER peptide transporter)- and ERAAP (ER-associated amino-peptidase)-independent. Surprisingly, both TAP and ERAAP either diverted or destroyed pHY and pLLO thereby reducing their presentation to TH cells. These finding led to two critical questions: (a) does the class I Ag processing (CAP) machinery globally impact class II-restricted Ag presentation; and (b) how do cytosolic Ags gain access to the endo/lysosomes for indirect presentation? In trying to understand how the cytosolic pHY returned to the endo/lysosomes for presentation, we ruled out the role for macro-autophagy as indirect presentation of HY proceeded in mice in which dendritic cells were conditionally deficient for Atg5. Instead, we found that the homodimeric TAP-like (TAP-L)-an orphan endo/lysosomal peptide transporter distinct from ER- resident TAP1/TAP2-was needed for indirect pHY presentation. Predicated on our functional studies, herein, we seek to gain biochemical insights into indirect presentation mechanism(s). Hence, we will test the central hypothesis that the class I Ag processing machinery regulates the pool of certain cytosolic Ags available for class II-restricted indirect presentation. Such Ags are processed in the cytosol and transported to the endo/ lysosomes in a TAP-L-dependent mechanism. To test this hypothesis, we will (a) determine whether the CAP machinery globally impacts H2Ab-restricted processing and presentation of self- or microbe-derived cytosolic Ags; (b) determine how cytosolic Ags enter the endo/lysosomes for indirect presentation; and (c) determine whether the CAP machinery impacts cytosolic Ag specific CD4+ T cell repertoire. Successful completion of this work will yield new biochemical insight(s) into indirect Ag presentation by class II molecules. A mechanistic understanding of class II-restricted indirect Ag presentation is critical not only for developing ways to circumvent/treat GvHD but also for vaccine design as this process is operative in the presentation of cytosolic Ags (viral, bacterial, parasitic) to TH cells and, hence, for vaccine design against tumours and pathogens.