MICROBIAL ANTIGENS IN CROHN'S DISEASE

克罗恩病候选微生物抗原的致病和保护的免疫机制。共生菌是人类克罗恩病和小鼠IBD模型中的重要疾病因素。这一见解提出了两个关键问题，新兴的研究：免疫发病机制的CD介导的反应，特别是肠道微生物？和，可以通过操纵这些反应产生现在-炎症或抗炎免疫.在上一个资助期，我们实验室成功应用免疫学和消减克隆方法鉴定了一组与UC和CD相关的细菌菌种和微生物抗原。这一更新申请的重点是这些候选人之一，I2，一个新的基因的细菌起源发现本地化的CD病变。I2编码蛋白的重组表达揭示了人CD中高度疾病特异性抗体水平。在小鼠中，证明了对I2的天然记忆T细胞免疫，并且在结肠炎敏感和抗性小鼠品系中效应器谱分别极化为TH 1和TH 2。这些发现支持该细菌作为CD的候选病原体，并提供了在实验室小鼠品系中评价候选人CD病原体的微生物学和免疫应答的独特机会。我们的更新项目检验了两个假设。首先，我们预测I2细菌是克罗恩病病原微生物亚群之一，因为它能够定殖相关粘膜部位并引起局部组织破坏性粘膜部位，并在易感宿主中引起局部组织破坏性免疫应答。我们将通过分离和鉴定I2细菌的分类学、毒力特征和肠组织分布来实验性地接近这一假设。从免疫学的角度来看，我们将评估肽特异性，个体发育，解剖起源，和致病性的T细胞群和细胞系特异性的I2抗原。其次，我们预测这种或其他抗原肠道微生物和粘膜自身抗原是抗炎T细胞的目标，这些T细胞是结肠炎的自然和治疗保护所必需的。我们将通过表征这些T细胞群体的个体发育和定位来实验性地测试这一假设;分离抗原特异性抗炎T细胞群体并评估其在结肠炎转移模型中的保护作用;以及测试抗原转移策略作为模型结肠炎的治疗性免疫调节剂。这些目标将取决于与项目4（小鼠中致病性和保护性粘膜T细胞群的细胞和拓扑学发育）、项目2（项目3衍生微生物抗原特异性人B和T细胞克隆群的表征）和项目1（与这些抗微生物应答相关的人类遗传基因座）的共同研究。

Immune mechanisms of Pathogenesis and Protection for Crohn's Disease Candidate Microbial Antigens. Commensal bacteria are an important disease factor in human Crohn's disease and murine IBD models. This insight raises two critical issues for emerging research: Is immune pathogenesis of CD mediated by responses to particular enteric microorganisms? And, Can these responses by manipulated to yield now- inflammatory or anti-inflammatory immunity. In the previous grant period, our laboratory successfully applied immunologic and subtractive cloning approaches identify a set of bacterial species and microbial antigens associated with UC and CD. This renewal application focuses on one of these candidates, I2, a novel gene of bacterial origin found to be localized in CD lesions. Recombinant expression of the I2-encoded protein revealed highly disease-specific antibody levels in human CD. In the mouse, native memory T cell immunity to I2 was demonstrated, and the effector profiles were polarized to TH1 and TH2 in colitis susceptible and resistant mouse strains, respectively. These finding support the bacterium as a candidate pathogen in CD, and present the unique opportunity to evaluate the microbiology and immune response for a candidate human CD pathogen in laboratory mouse strains. Our renewal project tests two hypotheses. First, we predict that the I2 bacterium exemplifies one of the subset of microorganisms pathogenic in Crohn's disease, due to its capacity to colonize relevant mucosal sites and elicit a local tissue-destructive mucosal sites and elicit a local tissue-destructive immune response in susceptible hosts. We will experimentally approach this hypothesis by isolating and characterizing the I2 bacterium with regard to taxonomy, virulence traits, and intestinal tissue distribution. From an immunologic perspective, we will evaluate the peptide specificity, ontogeny, anatomic origin, and pathogenicity of T cell populations and cell lines specific for the I2 antigen. Second, we predict that this or other antigen commensal microorganisms and mucosal autoantigens are targets of anti-inflammatory T cells necessary for the natural and therapeutic protection to colitis. We will experimentally test this hypothesis by characterizing the ontogeny and localization of these T cell populations; isolating antigen-specific anti-inflammatory T cell populations and evaluating their protective effect in colitis transfer models; and, testing antigen-transfer strategies as therapeutic immunomodulators of model colitis. These aims will depend on shared studies with Project 4 (cellular and topologic development of pathogenic and protective mucosal T cell populations in the mouse), Project 2 ( characterization of human B and T cell clonal populations specific for Project 3-derived microbial antigens), and Project 1( human genetic loci associated with these anti-microbial responses).