ROLE OF HLA-B27 IN EXPERIMENTAL SPONDYLOARTHROPATHY

HLA-B27是一种人类I类MHC等位基因，在被称为脊椎关节病（SpA）的风湿病患者中发现的患病率显著增加。有令人信服的证据表明，B27分子，通常是免疫系统的正常组成部分，本身参与了SPA的发病机制。确定B27在SpA发病机制中的分子作用，将是对慢性特发性炎症性疾病发病机制认识的重大进展。本申请描述了一个项目，该项目将在动物模型中研究B27在SpA中的作用，即转基因HLA-B27的大鼠。这些大鼠会自发患上一种疾病（rSpA），在许多基本方面与人类的SpA相似。研究的重点将是比较具有rSpA的B27转基因大鼠和其他不具有rSpA的相同近交系的大鼠。这两种株系之间唯一的遗传差异是B27转基因的拷贝数和B27的表达水平。关于B27在SpA中的作用，一个有吸引力的假设是，它以启动或放大致病性免疫反应的方式向CD8 T细胞提供一种或多种肽，这一作用与B27的生理功能有关。然而，最近有研究表明，与其他HLA I类分子相比，人体内的B27在生物合成中有时可能表现出不寻常的行为。据推测，这种不寻常的行为可能是SpA发病机制的一个关键特征。在这个项目中，这些假设将在转基因B27的大鼠中得到验证。在Specific Aim I中，将详细比较易感系和抗病系B27合成和降解的生化过程。在Specific Aim II中，一种结合细胞溶解T细胞、高效液相色谱和质谱的灵敏方法将被用于寻找B27在疾病易发品系中特异性呈现的肽。在Specific Aim III中，将应用一种基于MHC和肽特异性的CD8 T细胞鉴定和纯化的新方法，利用Specific Aim II的肽信息，在易发疾病的细胞系中鉴定潜在致病性T细胞。这些研究结果应该为B27在疾病发病机制中的作用提供实质性的新信息。如果机制涉及疾病相关肽，这些研究可能会确定它们。如果没有，这些研究应该有助于确定这一事实，并确定B27生物学的各个方面，其致病作用的基础。

HLA-B27 is a human class I MHC allele that is found with strikingly increased prevalence in patients with the rheumatic diseases termed spondyloarthropathies (SpA). There is persuasive evidence that the B27 molecule, ordinarily a normal component of the immune system, itself participates in the pathogenesis of SPA. It would represent a significant advance in the understanding of the pathogenesis of chronic idiopathic inflammatory diseases to identify the molecular role of B27 in the pathogenesis of SpA. This application describes a project in which the role of B27 in SpA will be studied in an animal model, namely, rats transgenic for HLA-B27. These rats spontaneously develop a disease (rSpA) that in many essential ways resembles human SpA. The focus will be on comparisons between lines of B27 transgenic rats that develop rSpA and other lines of the same inbred strains that do not. The only genetic difference between these two types of lines is the number of copies of the B27 transgene and the level of expression of B27. One attractive hypothesis for the role of B27 in SpA is that it presents one or more peptides to CD8 T cells in a manner that initiates or amplifies a pathogenic immune response, a role that is related to the physiologic function of B27. However, it has recently been shown that B27 in humans may sometimes exhibit unusual behavior in its biosynthesis, compared with other HLA class I molecules. It has been hypothesized that this unusual behavior may be a key feature to SpA pathogenesis. In this project, these hypotheses will be tested in the lines of rats transgenic for B27. In Specific Aim I, the biochemistry of B27 synthesis and degradation in the disease-prone and disease-resistant lines will be compared in detail. In Specific Aim II, a sensitive approach combining cytolytic T cells, HPLC, and mass spectrometry will be used to look for peptides presented by B27 specifically in the disease-prone lines. In Specific Aim III, a new methodology for identifying and purifying CD8 T cells on the basis of MHC and peptide specificity will be applied, using the peptide information of Specific Aim II, to identify potentially pathogenic T cells in disease-prone lines. The results of these studies should provide substantial new information regarding the role of B27 in disease pathogenesis. If the mechanism involves disease-associated peptides, these studies are likely to identify them. If not, these studies should help establish this fact and identify the aspects of B27 biology that underlie its pathogenic role.