THYMIC EXPRESSION OF PERIPHERAL AUTOANTIGENS IN AUTOIMMUNE DISEASE

与其在中枢耐受中的作用（对大量表达的自身抗原无反应性）相反，胸腺对外周耐受（对仅最低限度表达和/或仅由一个或几个器官表达的自身抗原的耐受）的贡献并不好 明白因此，本研究的长期目标是确定胸腺内自身抗原表达的减少或丧失是否有助于外周耐受的失败和自身免疫性疾病的诱导。作为实现这一目标的第一步，我们将把我们的努力集中在一个独特的动物模型上，即表达人C- 反应蛋白（CRP）转基因作为新自身抗原。尽管最近报道CRP转基因（CRPtg）小鼠由于胸腺表达转基因而耐受人CRP，但老年CRPtg/BW小鼠表达高滴度的血清抗人CRP自身抗体。这与SLE患者的情况相似。我们假设，在BW小鼠中， 由于胸腺表达受损，CRP和其他“器官特异性”外周抗原加速。为了验证这一假设，我们将集中精力在三个具体目标上。1)我们将确定外周自身抗原在自身免疫小鼠和正常小鼠胸腺表达的时间过程。 候选自身抗原CRP、髓鞘碱性蛋白的胸腺表达 (MBP)、Fas配体（FasL）和甲状腺球蛋白将对不同年龄的雌性小鼠进行定量。将比较自身免疫性CRPtg/BW与非自身免疫性CRPtg菌株（CRPtg/NZW和CRPtg/B6）中的胸腺表达。 2)我们将确定是否胸腺内和胸腺外表达 外周自身抗原受到不同的调节。将比较CRPtg BW、NZW和B6小鼠的CRP和血清淀粉样蛋白P组分的组成性和诱导性肝脏与胸腺表达。内毒素、IL-6和睾酮将用于诱导。3)我们将确定自身免疫的发展是否与胸腺抗原表达受损一致。将测定CRPtg/BW小鼠的血清CRP表达、抗CRP自身抗体应答的发展和T细胞对人CRP的应答的时间过程。将在老年CRPtg/BW小鼠中通过实验诱导人CRP的胸腺表达，以确定这是否延迟抗CRP应答。这些研究提供了一个独特的机会，记录自发丧失的耐受性，外周自身抗原通常耐受通过胸腺内表达。 胸腺中组织特异性基因表达水平不足，导致自身耐受性受损，可能是疾病的常见机制。

In contrast to its role in central tolerance (nonresponsiveness toward abundantly expressed self antigens), the contribution of the thymus to peripheral tolerance (tolerance to self antigens that are only minimally expressed and/or are expressed by only one or a few organs) is not well understood. Thus the long-term objective of the proposed research is to determine if reduction or loss of intrathymic expression of self antigens contributes to failure of peripheral tolerance and induction of autoimmune disease. As an initial step towards this objective we will focus our efforts on a unique animal model, i.e. Iupus-prone BW mice that express a human C- reactive protein (CRP) transgene as a neo-self antigen. Despite recent reports that CRP-transgenic (CRPtg) mice tolerate human CRP due to thymic expression of the transgene, aged CRPtg/BW mice express high titers of serum anti-human CRP autoantibodies. This mimics the situation seen in patients with SLE. We hypothesize that in BW mice the loss of tolerance to CRP and other 'organ-specific' peripheral antigens is accelerated due to compromised thymic expression. To test this hypothesis we will focus our efforts on three specific aims. 1) We will determine the time-course of thymic expression of peripheral autoantigens in autoimmune versus normal mice. Thymic expression of the candidate autoantigens CRP, myelin basic protein (MBP), Fas ligand (FasL), and thyroglobulin will be quantitated for female mice of various ages. Thymic expression in autoimmune CRPtg/BW versus nonautoimmune CRPtg strains (CRPtg/NZW and CRPtg/B6) will be compared. 2) We will determine if intra and extrathymic expression of peripheral autoantigens are differentially regulated. Constitutive and induced hepatic versus thymic expression of CRP and serum amyloid P-component will be compared for CRPtg BW, NZW, and B6 mice. Endotoxin, IL-6, and testosterone will be used for inductions. 3) We will determine if development of autoimmunity coincides with compromised thymic expression of antigens. The time-course of serum CRP expression, development of the anti-CRP auto-antibody response, and T-cell responsiveness to human CRP will be determined for CRPtg/BW mice. Thymic expression of human CRP will be induced experimentally in aged CRPtg/BW mice to determine if this delays the anti-CRP response. These studies provide a unique opportunity to document the spontaneous loss of tolerance to a peripheral self-antigen normally tolerated via intrathymic expression. Inadequate levels of expression of tissue-specific genes in the thymus, causing impaired self tolerance, might be a common mechanism of disease.