Mechanisms driving extrafollicular polyreactive B cell lineages in partial RAG deficiency

项目总结 患有先天性免疫缺陷的患者，如部分合并免疫缺陷(CID) 重组酶激活基因(RAG)缺乏症(PRD)易发生慢性感染，且难治性 自身免疫性疾病。RAG1/2是创造和审查B细胞受体多样性的关键。在珠三角的情况下， 发育中的自然具有自身反应的B细胞可能会在外围保持对自身的反应，无法 安装有效的抗体应答。这会导致慢性抗原暴露，从而激活T和B细胞。 我们建议关注两个特定的细胞群体：过度活跃的T滤泡辅助细胞(TFH)和先天样细胞 卵泡外多反应B细胞，作为自身免疫的标志物。后者类似于年龄相关的B细胞 (ABC)，随着感染和年龄的增加而积累。正常情况下，ABC对先天免疫高度敏感 由微生物和炎性细胞因子刺激，并在控制病毒感染方面发挥关键作用 产生保护性抗体。感染消退后，ABC数字明显收缩。但是，有了 慢性感染，ABC或ABC样细胞扩张、持续并产生保护性较差的抗体 对微生物和对自身的反应更强，特别是在有特殊遗传免疫缺陷的人身上。 多反应性ABC的持续扩增与微生物/抗原负荷(Toll样受体刺激)和 分泌炎性细胞因子干扰素和白介素21的TFH细胞的扩增 (IL-21)。目前尚不清楚哪些刺激和细胞信号通路在促进ABC自身反应方面起主导作用 我们的长期目标是了解自身反应性ABC是如何在CID中出现的，以便 开发有效的免疫调节治疗方法。我们假设人类对感染的易感性 PRD患者的结果是持续增加的微生物/抗原存在和慢性低级别 全身发炎。作为响应，TFH细胞大量分泌炎性细胞因子(干扰素和 IL-21)，它与慢性微生物刺激一起诱导ABC样细胞扩张并成为 分泌自身抗体的细胞，并将自身抗原呈递给支持它们的TFH细胞。因此，类ABC细胞 丰富性和自身反应性在珠江三角洲是永恒的。我们的具体目标是1)确定ABC的可能驱动因素- PRD患者中的类细胞和2)剖析促进ABC类细胞生成和持续的机制 使用PRD鼠标模型。我们的创新研究策略包括研究珠三角的国际队列 患者同时使用新的小鼠模型，将小鼠暴露在不同水平的微生物中，以及 ABC发育特征和自身免疫严重程度与基因表达变化的关系 病人。我们提出的研究具有重要意义，因为它可能会阐明功能失调的ABC样细胞是如何 在易受慢性感染的人群中发生，并导致改变特定B细胞信号的治疗 PRD和其他CID提高体液免疫和降低自身免疫的途径。

PROJECT SUMMARY Patients with congenital immunodeficiencies, such as combined immunodeficiencies (CID) with partial recombinase activating gene (RAG) deficiency (pRD) are highly vulnerable to chronic infections and refractory autoimmune disorders. RAG1/2 are key to creating and censoring the B cell receptor diversity. In case of pRD, developing B cells that are naturally autoreactive may remain reactive to self in the periphery and be unable to mount efficient antibody responses. This results in chronic antigen exposure that can activate T and B cells. We propose to focus on two specific cell populations: hyperactive T follicular helper (Tfh) cells and innate-like extrafollicular polyreactive B cells, as markers of autoimmunity. The latter resemble age-associated B cells (ABCs), which accumulate with infections and with age. Normally, ABCs are highly sensitive to innate immune stimulation by microbes and inflammatory cytokines and play a key role in controlling viral infections by producing protective antibodies. After the infection resolves, ABC numbers contract markedly. However, with chronic infections, ABCs or ABC-like cells expand, persist and produce antibodies that are less protective against microbes and more reactive to self, especially in individuals with particular genetic immunodeficiencies. Sustained expansion of polyreactive ABCs parallels microbial/antigen load (toll-like receptor stimulation) and expansion of Tfh cells, which secrete the inflammatory cytokines, interferon gamma (IFNand interleukin 21 (IL-21). It is unclear which stimuli and cell signaling pathways are dominant in promoting ABC autoreactivity in pRD or other CID s. Our long-term goal is to understand how autoreactive ABCs emerge in CID in order to develop effective immune modulatory treatments. We hypothesize that the susceptibility to infections of patients with pRD results in increased, continual microbial/antigen presence and chronic low-grade inflammation throughout the body. In response, Tfh cells secrete inflammatory cytokines abundantly (IFNand IL-21), which together with chronic microbial stimulation induces ABC-like cells to expand and become autoantibody-secreting cells and present autoantigens to Tfh cells, which sustains them. Thus, ABC-like cell abundance and autoreactivity is perpetuated in pRD. Our specific aims are to 1) identify likely drivers of ABC- like cells in pRD patients and 2) dissect mechanisms contributing to ABC-like cell generation and persistence using pRD mouse models. Our innovative research strategies include studying an international cohort of pRD patients in parallel with using novel mouse models, exposing mice to varying levels of microbes, and correlating gene expression changes with ABC developmental characteristics and autoimmune severity of patients. Our proposed study is significant because it will likely illuminate how dysfunctional ABC-like cells develop in persons susceptible to chronic infections and lead to therapies that modify specific B cell signaling pathways to improve humoral immunity and reduce autoimmunity in pRD and other CID.