Role of B cells in pathogenesis of Collagen-induced Arthritis in Humanized Mice

描述(申请人提供)：类风湿性关节炎(RA)及其动物模型胶原诱导性关节炎(CIA)是已知的T和B细胞依赖性疾病。人类白细胞抗原DQ8和DRB1*0401分子使人类和小鼠易患关节炎，而DQ6和DRB1*0402则提供保护。CIA易感的HLA转基因小鼠产生与患者相似的类风湿因子和抗环瓜氨酸肽(CCP)抗体。在B细胞基因敲除小鼠中缺乏CIA和低细胞反应表明，自身反应性B细胞除了产生抗体外，还可能参与向T细胞递送自身抗原。患者B细胞耗尽后ACR反应标准的改善进一步强调了B细胞在关节炎中的作用。然而，在转基因小鼠的敏感和耐药品系中，B细胞在抗原呈递和它们的调控中的确切作用仍不清楚。B细胞功能受B细胞受体BCR以及其他B细胞特异性受体如BAFF-R的调节。我们的假设是，携带RA易感基因的转基因小鼠的B细胞存在调控缺陷，这种缺陷是通过B细胞受体导致自身反应性B细胞过度活跃和存活增加的。女性有高度活跃的B细胞，这有助于自身抗体的产生和将抗原呈递给T细胞，从而增加女性的发病率。我们的初步数据与这一概念是一致的。最近的研究表明，B细胞的反应受TLRs控制。在这项研究中，我们将利用同时表达CIA敏感和耐药基因的转基因小鼠，探讨B细胞在胶原性关节炎发病机制中的作用机制。在AIM 1中，我们将明确B细胞在CIA发病机制中作为抗原提呈细胞的要求。在目标2中，我们将检验我们的假设，如果B细胞反应过度活跃和表位扩散在遗传易感小鼠中导致致病反应。此外，由于并不是所有RA易感等位基因阳性的转基因小鼠都会患关节炎，因此将确定那些患关节炎的转基因小鼠与不患关节炎的转基因小鼠在B细胞激活状态方面的潜在差异。在目标3中，我们将确定Toll样受体，特别是TLR4在该模型中对B细胞反应的控制。这些转基因小鼠和实验应该提供B细胞背景下的发病机制，并缩小B细胞导向治疗的范围。与公共卫生相关：类风湿性关节炎是一种致残性疾病，女性比男性更容易受到影响。B细胞产生类风湿因子和其他自身抗体。在这项研究中，我们将使用表达人类关节炎相关基因的小鼠来描述B细胞在类风湿关节炎患者中的作用。这些人源化的小鼠在病理和性别偏见上模仿类风湿性关节炎。关节炎小鼠产生自身抗体，如类风湿因子和抗环瓜氨酸肽抗体，用于诊断类风湿性关节炎。我们将确定B细胞是否能呈递致病抗原，以及在关节炎易感小鼠中，B细胞是否存在调节缺陷。使用这一独特模型获得的信息可能对开发针对持续性关节炎的预防性免疫干预具有指导意义，尤其是在女性中。

DESCRIPTION (provided by applicant): Rheumatoid arthritis (RA) and its animal model collagen-induced arthritis (CIA) are known to be T and B cell dependent diseases. HLA-DQ8 and DRB1*0401 molecules render humans and mice susceptible to develop arthritis while DQ6 and DRB1*0402 provide protection. CIA susceptible HLA transgenic mice produce rheumatoid factor and anti-cyclic citrullinated peptide (CCP) antibodies similar to that in patients. Absence of CIA and low cellular responses in B cell knockout mice suggests that the autoreactive B cells, in addition to producing antibodies may also be involved in presenting auto antigens to T cells. Improvement in ACR response criteria after depletion of B cells in patients further underscores the role of B cells in arthritis. However, the exact role of B cells in antigen presentation and their regulation in susceptible versus resistant strains of transgenic mice remains unclear. B cell function is regulated by B cell receptor, BCR, as well as other B cell specific receptors like BAFF-R. Our hypothesis is that B cells in transgenic mice carrying RA susceptible HLA gene have a defect in regulation which occurs through B cell receptor leading to hyperactivity and increased survival of autoreactive B cells. Females have hyperactive B cells which contribute towards the development of autoantibodies and presentation of antigens to T cells leading to increased incidence in females. Our preliminary data is consistent with this notion. Recent studies have shown that B cell responses are controlled by TLRs. In this study we will address the mechanism by which B cells contribute towards pathogenesis of collagen-induced arthritis in transgenic mice using mice expressing both CIA-susceptible and resistant HLA genes. In aim1, we will define the requirement of B cells as antigen presenting cells in pathogenesis of CIA. In aim 2 we will test our hypothesis if hyperactivity of B cell responses and epitope spreading in genetically susceptible mice leads to pathogenic response. Also, since not all transgenic mice positive for RA susceptible allele develop arthritis, potential differences in B cell activation status in those that develop arthritis versus that do not will be determined. In aim 3, we will determine the control of B cell responses by Toll like receptors, especially, TLR4 in this model. These transgenic mice and experiments proposed here should provide a mechanism of pathogenesis in context of B cells and narrow the focus of B cell-directed therapy. PUBLIC HEALTH RELEVANCE: Rheumatoid arthritis is a disabling disease, affecting women more often than men. B cells produce rheumatoid factor and other autoantibodies. In this study we will use mice that express human arthritis associated genes to delineate the role of B cells in rheumatoid arthritis patients. These humanized mice mimic rheumatoid arthritis in pathology and sex-bias. Arthritic mice produce autoantibodies like rheumatoid factor and anti-cyclic citrullinated peptide antibodies that are used for diagnosis of rheumatoid arthritis. We will determine if B cells can present pathogenic antigen and if there is a defect in regulation of B cells in arthritis susceptible mice. The information gained using this unique model may be instructive in developing preventive immunointervention for ongoing arthritis especially in women.