B cells in CNS autoimmunity

描述（由申请人提供）：B细胞在中枢神经系统自身免疫性疾病的发病机制中可能具有多种作用。虽然数据表明髓磷脂特异性抗体（Ab）促进实验性自身免疫性脑脊髓炎（EAE）和MS的脱髓鞘，但B细胞在CNS自身免疫性疾病中抗原（Ag）呈递中的作用尚不清楚。与其他APC群体相比，当B细胞表达针对应答T细胞识别的Ag特异性B细胞受体（BCR）时，B细胞是高效的Ag蛋白APC。我们假设B细胞，特别是髓磷脂特异性B细胞在髓磷脂特异性T细胞的激活中具有重要的APC作用。我们建议(1)评估髓磷脂特异性B细胞作为APC在EAE中的作用，并将其功能与髓磷脂特异性Ab在EAE中的作用区分开来。我们正在创建两种转基因（Tg）模型，一种含有只表达mog特异性BCR的B细胞，另一种含有表达mog特异性BCR并能分泌mog特异性IgM的B细胞。我们将比较这些小鼠与B细胞缺陷小鼠和mog特异性BCR敲入小鼠的EAE易感性，这些小鼠可以分泌所有Ig同种型。我们建议(2)研究B细胞MHC II表达和髓磷脂BCR特异性在EAE中髓磷脂Ag呈递中的作用。我们假设B细胞，特别是髓鞘特异性B细胞，在EAE和ms中MHC II限制性Ag呈递和髓鞘特异性T细胞激活中作为APC发挥关键作用(a)。我们将通过创建混合bm嵌合体小鼠来测试MHC II限制性B细胞Ag呈递到T细胞的作用，其中B细胞区室选择性地缺乏MHC II表达。并比较mog特异性T细胞的活化和EAE对含有表达MHC II分子的B细胞的bm嵌合体小鼠的易感性。(b)为了阐明BCR特异性在EAE中MHC II限制性Ag呈递中的作用，我们将检测混合bm嵌合体小鼠，其中b细胞表达mog特异性BCR或硝基苯（NP）特异性BCR，并表达或不表达MHC II分子。最近的临床结果表明，抗cd20b细胞清除可能在多发性硬化症治疗中有效。我们的初步数据表明，B细胞耗竭对rmog诱导的EAE有益，但会加剧MOG p35- 55诱导的EAE。我们假设rmog诱导的EAE的临床获益是由于B细胞Ag呈递减少或髓鞘特异性Ab分泌减少。我们还假设MOG p35-55诱导的EAE（一种较少依赖B细胞和Ab的模型）的恶化代表了B细胞调节功能的丧失。为了评估这些可能性，我们将(3)研究抗cd20 B细胞耗竭如何影响急性和慢性EAE外周和中枢神经系统中mog特异性T细胞反应，并研究mog特异性Ab反应是否与抗cd20 B细胞耗竭小鼠的临床改善相关。这些研究应该提供关于中枢神经系统自身免疫中B细胞消耗的机制见解，并解决在MS临床试验中不易接近的关于B细胞消耗的问题。B淋巴细胞可能在多发性硬化症（MS）的发病机制中发挥多种作用，多发性硬化症是一种中枢神经系统（CNS）自身免疫性疾病。我们对实验性自身免疫性脑脊髓炎（EAE）的研究，即小鼠MS模型，将评估和区分B细胞在中枢神经系统自身免疫中的潜在致病作用。我们的研究项目还将评估抗cd20 B细胞消耗（一种正在MS临床试验中研究的治疗方法）如何影响免疫调节。第5页

DESCRIPTION (provided by applicant): B cells may have multiple roles in pathogenesis of CNS autoimmune disease. While data indicate that myelin-specific antibodies (Ab) promote demyelination in experimental autoimmune encephalomyelitis (EAE) and MS, the role of B cells in antigen (Ag) presentation in CNS autoimmune disease is not clear. When compared to other APC populations, B cells are efficient APC in presentation of protein Ag when they express the B cell receptor (BCR) specific for the Ag recognized by responding T cells. We hypothesize that B cells, in particular, myelin-specific B cells have an important role as APC in activation of myelin-specific T cells. We propose (1) to evaluate the contribution of myelin-specific B cells as APC in EAE and distinguish this function from the role of myelin-specific Ab in EAE. We are creating two transgenic (Tg) models, one containing B cells that express membrane MOG-specific BCR only, and one containing B cells that express membrane MOG-specific BCR and can secrete MOG-specific IgM. We will compare EAE susceptibility in these mice to B cell-deficient and MOG-specific BCR knock-in mice that can secrete all Ig isotypes. We propose (2) to examine the roles of B cell MHC II expression and myelin BCR specificity in presentation of myelin Ag in EAE. We hypothesize that B cells, in particular myelin-specific B cells, have a key role as APC in MHC II-restricted Ag presentation and activation of myelin-specific T cells in EAE and MS. (a) We will test the role of MHC II-restricted B cell Ag presentation to T cells by creating mixed bm chimera mice in which the B cell compartment is selectively deficient in MHC II expression, and compare activation of MOG-specific T cells and EAE susceptibility to bm chimera mice containing B cells that express MHC II molecules. (b) To clarify the role of BCR specificity in MHC II-restricted Ag presentation in EAE, we will examine mixed bm chimera mice in which B cells express either the MOG-specific BCR or nitrophenyl (NP)-specific BCR and do, or do not, express MHC II molecules. Recent clinical results suggest that anti-CD20 B cell depletion may be effective in MS treatment. Our preliminary data suggest that B cell depletion is beneficial in rMOG-induced EAE, but exacerbates MOG p35- 55-induced EAE. We hypothesize that the clinical benefit in rMOG-induced EAE results from reduced B cell Ag presentation or decreased secretion of myelin-specific Ab. We also hypothesize that exacerbation of MOG p35-55-induced EAE, a model that is less dependent upon B cells and Ab, represents loss of regulatory B cell function. In order to evaluate these possibilities, we will (3) examine how anti-CD20 B cell depletion influences MOG-specific T cell responses in the periphery and in the CNS in acute and chronic EAE, and examine whether MOG-specific Ab responses correlate with clinical improvement in anti-CD20 B cell-depleted mice. These studies should provide mechanistic insight regarding B cell depletion in CNS autoimmunity and address questions regarding B cell depletion that are not easily approached in MS clinical trials. PUBLIC HEALTH RELEVANCE B lymphocytes may have multiple roles in the pathogenesis of multiple sclerosis (MS), a central nervous system (CNS) autoimmune disease. Our studies in experimental autoimmune encephalomyelitis (EAE), the murine MS model, will evaluate and distinguish potentially pathogenic roles of B cells in CNS autoimmunity. Our research program will also evaluate how anti-CD20 B cell depletion, a therapeutic approach being investigated in MS clinical trials, may influence immune regulation. Page 5