Regulatory B cells in multiple sclerosis - functional characterization and therapeutic implication

多发性硬化症(MS)是一种中枢神经系统炎症性脱髓鞘疾病，其残疾可以作为急性复发或持续的慢性恶化发生。在其发病机制中，B细胞及B细胞衍生产物可能起关键作用；在许多MS患者中，外周血B细胞呈现慢性激活和促炎分化的迹象。在脑脊液中，克隆扩增的浆细胞产生寡克隆免疫球蛋白，这仍然是一个标志性的诊断发现。此外，在最近的MS临床试验中，抗CD20介导的B细胞耗尽阻止了中枢神经系统病变的发展，并减少了复发的发生。除了这些证明其致病作用的证据外，B细胞可能在MS中发挥抗炎特性，在MS患者中，与健康对照组相似，B细胞是调节细胞因子的相关来源，如IL-10，它抑制其他免疫细胞的活性。在MS模型实验性自身免疫性脑脊髓炎(EAE)中，缺乏释放调节性B细胞细胞因子的小鼠无法从急性发作中恢复，相反，小鼠的病情会慢性恶化。因此，B细胞在新生中枢神经系统浸润引起的复发的发生发展中起着至关重要的作用，但仍传递着促进恢复和防止向慢性进展过渡的潜力。为了破解这一具有广泛临床意义的明显谜团，我们将从功能上描述并可能描述MS患者致病B细胞特性中的调节B细胞功能。首先，我们将表征MS患者中枢神经系统组织中的B细胞和浆细胞。通过我们研究所开发的成像技术，这些研究现在成为可能。结合转录组分析，我们将调查MS病变中的所有B细胞是否都是统一致病的，以及患者或中枢神经系统病变的亚型是否会在致病B细胞与调节B细胞的程度上有所不同(目标1)。其次，我们将确定MS患者外周血促炎症B细胞和抗炎B细胞的相对程度是否不同。我们将把这种个体B细胞表型与IL-10的丧失和抗CD20治疗后促炎症单核细胞功能的相对增强联系起来。从前瞻性和与临床结果的相关性来看，这些免疫学参数可以发展成为预测个体对抗CD20治疗的反应的迫切需要的生物标志物(目标2)。最后，我们将在EAE中调查B细胞是否、在哪里以及如何促进恢复和控制慢性进展。为此，我们利用了一种纯T细胞介导的EAE模型，在该模型中，抗CD20抗体显著恶化了疾病的严重程度。利用这一模型，结合转基因B细胞的过继转移和跟踪，我们将研究B细胞在多大程度上可以抑制中枢神经系统内在的炎症循环，假定的进展相关性，以及需要哪些B细胞特性来调节这一效应(目标3)。

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system, in which disability can occur as acute relapses or as continuous chronic deterioration. In its pathogenesis, B cells and B cell-derived products may play a key role; in many MS patients, peripheral B cells show signs of chronic activation and pro-inflammatory differentiation. In the cerebrospinal fluid, clonally expanded plasma cells produce oligoclonal immunoglobulins, which remain a hallmark diagnostic finding. Moreover, anti-CD20-mediated depletion of B cells halted development of CNS lesions and reduced occurrence of relapses in recent clinical MS trials. Besides such evidence for their pathogenic contribution, B cells may exert anti-inflammatory properties in MS. Naïve B cells, in MS patients similar to healthy controls, are a relevant source of regulatory cytokines, such as IL-10, which dampens the activity of other immune cells. Mice deficient in releasing regulatory B cell cytokines fail to recover from an acute attack in the MS model experimental autoimmune encephalomyelitis (EAE) and instead chronically deteriorate. B cells are thus crucially involved in development of relapses caused by de novo CNS infiltration, and yet convey the potential to promote recovery and to prevent transition to chronic progression. To decrypt this apparent enigma with wide-ranging clinical implications, we will functionally characterize and possibly delineate regulatory B cell function from pathogenic B cell properties in MS. At first, we will characterize B and plasma cells in CNS tissues from MS patients. These studies are now possible by an imaging technique developed at our Institute. In conjunction with transcriptome analyses, we will investigate whether all B cells in MS lesions are uniformly pathogenic, and whether subtypes of patients or CNS lesions may vary in the extent of pathogenic versus regulatory B cells (aim 1). Second, we will determine whether MS patients differ in the relative extent of peripheral pro- and anti-inflammatory B cells. We will correlate this individual B cell phenotype to the loss of IL-10 and the relative increase of pro-inflammatory monocyte function upon anti-CD20 treatment. In perspective and correlation with the clinical outcome, these immunological parameters could develop into an urgently needed biomarker predicting the individual response to anti-CD20 treatment (aim 2). Lastly, we will investigate in EAE, whether, where and how B cells promote recovery and control chronic progression. For this purpose, we are utilizing a purely T cell-mediated EAE model, in which anti-CD20 substantially deteriorates disease severity. Using this model in combination with adoptive transfer and tracking of genetically modified B cells, we will investigate to what extent B cells can dampen CNS intrinsic circuits of inflammation, the assumed correlate of progression and which B cell property is required to mediate this effect (aim 3).