Pathogenic T cells in chronic beryllium disease

描述(申请人提供)：对铍(Be)、镍(Ni)等金属离子的病理性免疫反应是人类T细胞介导的超敏反应最常见的原因之一，但阳离子呈递给T细胞受体(TCR)的性质尚不清楚。在这方面，慢性铍病(CBD)是一种由工作场所铍暴露引起的肺部肉芽肿性疾病，其特征是Be特异性CD4+T细胞在肺内积聚。CBD仍然是一个重要的公共卫生问题，有100多万美国工人暴露在铍中，并面临疾病发展的风险。遗传易感性与HLA-DP等位基因密切相关，这些等位基因在第69位含有谷氨酸(Glu69)，大多数CD4+T细胞以一种HLA-DP受限的方式识别BE。在之前的资助期间，我们结晶了最普遍的含有Glu69的人类白细胞抗原-DP分子-人类白细胞抗原-DP2，并表明其与人类白细胞抗原-DP2的多肽结合槽比其他MHCII分子更宽，打开了一个暴露在溶剂中的酸性口袋，其中包括谷氨酸69，并可以很容易地容纳含有Be的化合物。我们鉴定了一组相关的BE依赖多肽，它们与人类白细胞抗原DP2结合，并刺激来自CBD患者肺组织的CD4+T细胞上表达的BE特异性TCR。这些多肽在P4和P7具有带负电荷的天冬氨酸和谷氨酸残基，这些残基环绕在人类白细胞抗原DP2分子中推测的BE结合部位，在金属诱导的超敏反应中发挥着一种新的多肽功能，即金属离子捕获。该复合体的BE负载的HLADP2多肽四聚体主要与表达HLADP2的CBD患者肺组织中表达V5.1的CD4+T细胞结合。然而，这种配体只占肺中BE反应T细胞的~5%，这表明额外的多肽完成了大多数BE反应T细胞的TCR配体，并且每个BE依赖的配体可能被不同的表达TCRV的T细胞亚群识别。因此，我们假设BE依赖的多肽将在p4和p7表达一个独特的捕获和协调BE的酸性氨基酸的核心基序，并且这些BE依赖的配体中的每一个都将被一组不同的BE特异的CD4+T细胞识别。为了将我们的基础科学发现转化为一套可以识别疾病进展和监测严重程度的生物标记物，对这些未知的Be依赖多肽的鉴定是至关重要的。第一个特定的目标是识别更多的BE依赖的多肽，以完成一组BE特异性的CD4+T细胞的BE特异性TCR配体。在第二个目的中，我们将使用这些配体的HLA-DP2四聚体来质疑与这些试剂结合的BE特异性CD4+T细胞是否包括公共TCR谱系。在第三个具体目标中，我们将确定这些Be依赖配体的四聚体是否可以用作暴露于Be的受试者的疾病进展和严重程度的生物标志物。总之，这些研究将加强我们对抗原如何引起肉芽肿性炎症，特别是金属抗原如何触发免疫反应的理解。

DESCRIPTION (provided by applicant): Pathological immune responses to metal ions such as beryllium (Be), nickel (Ni), and others are among the most common causes of T cell-mediated hypersensitivities in humans, yet the nature of cation presentation to the T cell receptor (TCR) is unknown. In this regard, chronic beryllium disease (CBD) is a granulomatous lung disorder caused by beryllium exposure in the workplace and is characterized by the accumulation of Be- specific CD4+ T cells in the lung. CBD remains an important public health concern with more than 1,000,000 US workers having been exposed to beryllium and at risk for disease development. Genetic susceptibility is strongly linked to HLA-DP alleles that contain a glutamic acid at the 69th position of the ¿-chain (¿Glu69), and the majority of CD4+ T cells recognize Be in an HLA-DP-restricted manner. During the previous funding period, we crystallized HLA-DP2, the most prevalent ¿Glu69-containing HLA-DP molecule, and showed that its peptide-binding groove of HLA-DP2 was wider than that of other MHCII molecules, opening a solvent-exposed acidic pocket that included ¿Glu69 and could easily accommodate a Be-containing compound. We identified a set of related Be-dependent peptides that bind to HLA-DP2 and stimulate a Be-specific TCRs expressed on CD4+ T cells from the lung of a CBD patient. These peptides possess a negatively-charged aspartic and glutamic acid residues at p4 and p7 of the peptide, which surround the putative Be binding site in the HLA-DP2 molecule and serve a novel peptide function in metal-induced hypersensitivity, that being metal ion capture. Be-loaded HLA-DP2-peptide tetramers of this complex predominantly bind to V¿5.1-expressing CD4+ T cells from the lungs of HLA-DP2-expressing CBD patients. However, this ligand only accounts for ~5% of Be-responsive T cells in the lung, suggesting that additional peptides complete the TCR ligand for the majority of Be-responsive T cells and that each Be-dependent ligand may be recognized by a different TCR V¿-expressing T cell subset. Thus, we hypothesize that Be-dependent peptides will express a unique core motif of acidic amino acids at p4 and p7 that capture and coordinate Be and that each of these Be-dependent ligands will be recognized by a different set of Be-specific CD4+ T cells. The identification of these unknown Be-dependent peptides is essential in order to translate our basic science findings into a set of biomarkers that can identify disease progression and monitor severity. The first specific aim will identify additional Be-dependent peptides to complete the Be-specific TCR ligand for a set of Be-specific CD4+ T cells. Using HLA-DP2 tetramers of these ligands, we will query whether the Be-specific CD4+ T cells that bind to these reagents comprise public TCR repertoire in the second aim. In the third specific aim, we will determine whether tetramers of these Be-dependent ligands can be used as biomarkers of disease progression and severity in Be-exposed subjects. Together, these studies will strengthen our understanding of how antigens cause granulomatous inflammation and specifically how metals antigens trigger an immune response.