Human Transitional B Cells: Homeostasis, Function, and Impact of BCDT

项目总结（见说明）： B细胞在系统性红斑狼疮（SLE）和类风湿性关节炎（RA）的发病机制中起关键作用。一 项目I的主要焦点是确定骨髓发育线索和外周血过渡B细胞的更新 以及在系统性自身免疫中可能受到干扰的细胞因子环境如何调节这一过程。据推测 自身免疫性疾病与B细胞发育过程中过渡性B细胞稳态失调有关 随着从骨髓（BM）中出现的过渡性B细胞数量的改变， 调节这一过程的信号（IFN，TNF），以及进展到成熟区室的信号阈值 （BAFF）。另一方面，我们发现SLE患者的循环移行细胞显著扩张， B细胞耗竭治疗（BCDT）后的SLE和RA患者进入长期临床缓解，而SLE和RA患者 记忆重建越快，疾病复发越早。这一建议的重点是要及早了解 SLE和RA患者BCDT后B细胞稳态和调节B细胞重建的因素通过以下方式 具体目标将确定：1.自身免疫性疾病中人移行B细胞稳态的紊乱 2.sease;调节BCDT后不同B细胞亚群重建平衡的因子;和3.的 过渡性B细胞和调节性T细胞的相互调节以及在自身免疫性疾病中如何改变， BCDT之后具体来说，我们将使用B细胞耗竭作为工具来定义人类B细胞发育的动态 和多参数流式细胞术。过渡期B细胞的寿命和周转将通过重水进行评估 标记，复制历史，细胞周期，以及生存和选择的描绘。细胞因子环境对新生儿免疫功能的影响 将检查BM B细胞淋巴细胞生成。本项目将探讨BCDT的结果反映了 保护性（调节性、抗炎性）和效应性（前趋化性）B细胞之间的平衡以及它们的 相应的细胞因子。过渡性B细胞的功能包括产生抗炎 细胞因子如IL-10和TGFB以及支持调节性T细胞（Treg）发育。我们将定义人类是否 B细胞亚群差异性地支持Treg扩增或差异性地对Treg抑制敏感，如果该功能 自身免疫环境的变化，以及这些异常如何被BCDT修饰。阐明体内平衡 人过渡性B细胞的调节将代表人B细胞生物学的重大进展。研究提出， 这也将帮助我们了解B细胞发育在自身免疫性疾病中是如何失调的，以及消耗如何诱导 改善，在某些情况下，disea.se缓解。

PROJECT SUMMARY (See instructions): B cells play a critical role in the pathogenesis of systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). A major focus of Project I is to define the bone marrow developmental cues and peripheral turnover of transitional B cells and how cytokine milieu, which may be perturbed in systemic autoimmunity, regulates this process. It is hypothesized that autoimmune disease is as.sociated with dysregulation of transitional B cell homeostasis during B cell development with alterations in the numbers of transitional B cells emerging from the bone marrow (BM), the inicroenvironmenlal signals that modulate this process (IFN, TNF), and the signaling threshold for progression to the mature compartinent (BAFF). On the other hand, we have found that SLE patients with a prominent expansion of circulating transitional cells after B cell depletion therapy (BCDT) enter long-term clinical remission, whereas both SLE and RA patients with more rapid memory reconstitution experience earlier relapse of disease. The focus of this proposal is to understand early B cell homeostasis and the factors that regulate B cell reconstitution after BCDT in SLE and RA through the following specific aims which will define: 1. the perturbations in homeostasis of human transitional B cells in autoimmune di.sease; 2. the factors which regulate the balance of reconstitution of distinct B cell subsets after BCDT; and 3. the reciprocal regulation of transitional B cells and regulatory T cells and how this is altered in autoimmune disease and after BCDT. Specifically, we will define the dynamics of B cell development in humans using B cell depletion as a tool and multi-parameter flow cytometry. The lifespan and turnover of transitional B cells will be assessed by heavy water labeling, replication history, cell cycle, and delineation of survival and .selection. The effects of cytokine milieu on new BM B cell lyinphopoeisis will be examined. This project will explore the hypothesis that the outcome of BCDT rellects the balance between protective (regulatory, anti-inflammatory) and effector (prointlammatoiy) B cells and their corresponding cytokines. Transitional B cell functions to delineate include the production of anti-intlammatory cytokines such as IL-10 and TGFB and support of regulatory T cell (Treg) development. We will define whether human B cell subsets differentially support Treg expansion or are differentially susceptible to Treg suppression, if this function changes in autoimmune settings, and how these abnormalities are modified by BCDT. Elucidation of the homeostatic regulation of human transitional B cells will represent a major advance in human B cell biology. The research proposed will also help us understand how B cell development is dysregulated in autoimmune disease and how depletion induces improvement and, in some cases, long-lasting disea.se remission.