Role of B Cells in Synovial Inflammation & LN Remodeling in RA Arthritis

肿瘤坏死因子拮抗剂联合B细胞去除疗法治疗类风湿关节炎的疗效观察 从根本上改变了病理生理学范式，并提出了关于疾病机制的新问题。 观察到肿瘤坏死因子和B细胞都具有核心重要性，这为改善提供了强大的推动力 我们对肿瘤坏死因子过度产生与其介导的信息通路关系的认识 B细胞，特别是在疾病爆发和治疗反应不足方面。转基因肿瘤坏死因子 (肿瘤坏死因子-甘油三酯)小鼠株是唯一一个具有临床证实的病因的RA慢性进展性模型，因此对于研究RA的细胞和免疫学事件具有非常重要的价值。我们开发了一系列新的小动物成像方法，包括对比增强(CE)MRI、活体微型CT和近红外吲哚青绿(NIR-ICG)淋巴流动分析，以纵向研究与关节关节炎进展相关的事件。这些研究的结果，结合组织学和流式细胞术，显示在膝关节疾病发生之前和之后，引流杨淋巴结(PLN)在可预见的时间序列中发生了戏剧性的变化。对于膝关节滑膜炎，引流的PLN“扩张”，表现为体积和CE值的增加(即密度降低)，组织学表现为明显扩张、增大的血窦。这种结节扩张的特征也是PLN B细胞增多 数量，主要是由于具有独特表面表型的B细胞亚群的积累(“B-in”细胞)。在这一阶段之后，结节大小和CE迅速减小，B细胞侵袭和“堵塞”淋巴窦，通过结节的淋巴流量减少。PLN塌陷后出现膝关节滑膜炎和局灶性糜烂。BCDT和抗CXCL13治疗均可导致肿瘤坏死因子-甘油三酯病的PLN大小、CE和组织学的改善和恢复，表明B细胞和趋化细胞共同发挥致病作用。因此，我们假设，在肿瘤坏死因子-甘油三酯小鼠的膝关节炎和PLN功能的演变始于早期阶段，在此期间，致病的B细胞被招募到并在引流结节内积累，引流结节的大小和CE增加。在后来的阶段，PLN固有的或外部的(例如来自关节的)信号诱导扩大的B细胞群迁移到血窦间隙，导致淋巴流动受阻和局部细胞因子平衡的改变。这会导致促炎介质在膝关节内积聚，引发“耀斑”。在这里，我们建议通过以下方式来测试这一模型：1)确定导致B细胞在PLN中积聚并随后迁移到淋巴间隙的机制；2)展示过继转移的PLN B细胞的致病作用，并验证BCDT疗效与清除侵犯血窦的B细胞有关的假设；3)测试TNF-TG B细胞是否能发挥促炎效应功能；以及d)在一项试点临床试验中研究这些发现对RA患者的适用性，该临床试验将在BCDT前后对PLN的结构和淋巴功能进行评估，并与临床症状相关联。

The efficacy of TNF antagonists and B cell depletion therapy (BCDT) in rheumatoid arthritis (RA) have fundamentally altered pathophysiologic paradigms and raised new quesfions about disease mechanisms. The observation that both TNF and B cells are of central importance provides a strong impetus to improve our understanding ofthe relationship between TNF over-production and infiammation pathways mediated by B cells, particulady in regards to disease flares and inadequate treatment response. The TNF-transgenic (TNF-tg) mouse strain is the only chronically progressive model for RA with a clinically proven etiology, and thus invaluable to address the cellular and immunological events in RA. We have developed a series of novel small animal imaging approaches, including contrast enhanced (CE) MRI, in vivo micro-CT and nearinfrared indocyanin green (NIR-ICG) analysis of lymphatic flow, to study longitudinally the events associated with progression of joint arthritis. The results from these studies, combined with histology and flow cytometry, showed dramatic changes unfolding in a predictable temporal sequence in the draining popliteal lymph-node (PLN) before and duhng the onset of knee disease. Pnor to knee synovitis, the draining PLNs "expand", as evidenced by increased volume and CE values (i.e. lower density), and histology of the node shows markedly dilated, enlarged sinusoids. This nodal expansion is also characterized by increased PLN B cell numbers, primanly due to accumulation of a B cell subset with a unique surface phenotype ("B-in" cells). This phase is followed by a rapid decrease in node size and CE, by invasion and "plugging" ofthe lymphatic sinuses by B cells, and reduced lymphatic flow through the node. The onset of knee synovitis and focal erosions follows PLN collapse. Both BCDT and anti-CXCL13 treatment result in TNF-tg disease ameliorafion and recovery of PLN size, CE and histology, pointing to a pathogenetic role of both B cells and chemotaxis. Thus, we hypothesize that evolution of knee arthritis and PLN function in TNF-tg mice proceed from an early stage during which pathogenetic B cells are recruited to and accumulate in the draining nodes, which increase in size and CE. At a later stage PLN-intrinsic or external (e.g. from the joint) signals induce migration ofthe expanded B cell population to the sinusoidal spaces, resulting in the obstruction of lymph flow and changes in the local cytokine balance. This leads to accumulation of pro-inflammatory mediators in the knee joint, triggering the "flare". Here we propose to test this model by: 1) identifying the mechanisms that lead to B cell accumulation in the PLNs and their subsequent migration to lymphatic spaces; 2) demonstrating the pathogenetic role of adoptively transfered PLN B cells, and testing the hypothesis that BCDT efficacy is associated with clearance of sinusoid-invading B cells; 3) testing whether TNF-tg B cells can exert pro-inflammatory effector functions; and d) investigating the applicability of these finding to RA patients in a pilot clinical tnal in which PLN structure and lymphatic function wil be assessed before and after BCDT, and correlated with clinical svmptoms.