INNATE AND ADAPTIVE MECHANISMS IN ARTHRITIS

描述(申请人提供)：类风湿性关节炎导致严重的残疾和增加的死亡率。目前对其发病机制的研究主要集中在宿主免疫失调导致病理改变的机制上。巨噬细胞移动抑制因子(MIF)是天然免疫细胞(单核/巨噬细胞)和获得性免疫细胞(T细胞)产生的免疫反应的上游调节因子。我们发现人类MIF基因(MIF)是由功能不同的等位基因编码的，并且高表达的MIF等位基因在类风湿关节炎患者中过度表达。我们还鉴定了细胞表面蛋白CD74是MIF的细胞受体。我们认为MIF由先天或获得性免疫反应产生的过度产生及其与CD74的结合在类风湿关节炎的发病中起着内在的作用。本应用的目的是明确MIF在炎症性关节炎中产生和作用的细胞基础。中心假设是炎症性关节炎是由于单核/巨噬细胞或T细胞过度产生MIF，再加上MIF通过与CD74结合而激活靶细胞。这项拟议研究的基本原理是，一旦知道MIF在炎症性关节炎中产生和作用的分子基础，就会对这种疾病的免疫失调有更准确的了解。我们将通过追求三个具体目标来验证我们的假设并实现这一应用的目标：1)通过研究单核细胞特异性和T细胞特异性Mif-Knokout小鼠，确定MIF在炎症性关节炎中的作用。我们将检查MIF-FLOGED小鼠的关节炎发展情况，这些小鼠的单核细胞来源的MIF或T细胞来源的MIF存在遗传缺陷。2)确定MIF/CD74相互作用在体内的病理作用。我们将通过给实验性关节炎野生型小鼠注射中和抗CD74单抗或可溶性CD74蛋白(SCD74)来确定MIF/CD74相互作用的病理学重要性。3)明确高表达和低表达的Mif等位基因在人类单核细胞和T细胞的MIF产生、细胞激活和下游细胞因子表达中的作用。我们将获得类风湿关节炎患者的单核细胞和T细胞，分析MIF基因，并研究MIF的产生、细胞激活和下游细胞因子的表达。这些结果将具有重要意义，因为它们将提供对MIF在连接先天免疫和获得性免疫的途径中所起作用的更准确的理解，这些途径变得失调，从而产生炎症性关节炎。此外，它们将为根据Mif等位基因识别可能是严重类风湿性关节炎高危个体提供科学依据，以便采取措施更好地治疗他们的侵蚀性疾病。

DESCRIPTION (provided by applicant): Rheumatoid arthritis causes significant disability and increased mortality. Research into its pathogenesis currently focuses on the mechanisms by which host immunity becomes dysregulated to produce pathologic changes. Macrophage migration inhibitory factor (MIF) is an upstream regulator of the immune response that is produced both by innate (monocyte/macrophage) and adaptive (T cell) immune cells. We have discovered that the human MIF gene (Mif) is encoded by functionally distinct alleles, and that high-expression Mif alleles are over-represented in patients with rheumatoid arthritis. We also have identified the cell surface protein, CD74, to be a cellular receptor for MIF. We suggest that MIF overproduction by the innate or the adaptive immune response and its binding to CD74 play an intrinsic role in the pathogenesis of rheumatoid arthritis. The objective of this application is to define the cellular basis of MIF production and action in inflammatory arthritis. The central hypothesis is that inflammatory arthritis results from an overproduction of MIF by monocytes/macrophages or by T cells, coupled with MIF activation of target cells by binding to CD74. The rationale for this proposed research is that once the molecular basis for MIF production and action in inflammatory arthritis is known, then a more precise understanding of immune dysregulation in this disease will have been achieved. We will test our hypothesis and accomplish the objective of this application by pursuing three specific aims: 1) Define MIF's Role in Inflammatory Arthritis by Studying Monocyte-specific and T cell-specific Mif-Knockout Mice. We will examine arthritis development in Mif-floxed mice made genetically-deficient either for monocyte-derived MIF, or for T cell-derived MIF. 2) Establish the Pathologic Role of the MIF/CD74 Interaction In Vivo. We will establish the pathologic importance of the MIF/CD74 interaction by administering a neutralizing anti- CD74 mAb, or a soluble CD74 protein (sCD74), to wild-type mice with experimental arthritis. 3) Define the Role of High- versus Low-expression Mif alleles in MIF Production, Cellular Activation, and Downstream Cytokine Expression by Human Monocytes and T Cells. We will obtain monocytes and T cells from patients with rheumatoid arthritis, analyze the Mif genotype, and study MIF production, cellular activation, and downstream cytokine expression. These results will be significant because they will provide a more precise understanding of MIF's role in the pathways that link innate and adaptive immunity, and which become dysregulated to produce inflammatory arthritis. Moreover, they will provide a scientific rationale for identifying individuals who may be a high risk for severe rheumatoid arthritis - based on their Mif alleles, so that steps can be taken to better treat their erosive disease.