BCR-NF-κB与IL-4Rα-STAT6信号的合成协同构成功能性IgE类别转换重组的主检查点

文献信息

中文摘要

背景： 异常的免疫球蛋白E（IgE）类别转换重组（CSR）是全球流行的2型过敏性疾病的基础，影响全球数亿人。在稳态条件下，IgE产生受到严格限制，而IgG4和IgA的CSR则顺利进行；强制实施这种限制的分子机制仍未完全明确。BCR-NF-κB和IL-4Rα-STAT6均参与IgE相关的转录编程，但尚不清楚孤立的还是同时发生的通路活性驱动功能性IgE CSR。
目的： 在明确的实验条件下表征有效IgE CSR的分子阈值，并检验信号协同模型，同时探索潜在的相关临床观察和临床前治疗机会。
方法： 原代初始小鼠B细胞和人外周血来源的初始B细胞在恒定CD40L共刺激下培养，采用三种实验条件：孤立的BCR激活、孤立的IL-4Rα激活或双通路共激活。检测方法包括qPCR、ATAC-seq、ChIP-qPCR、邻位连接 assay（PLA）、序贯re-ChIP和流式细胞术，以定量胚系ε（GLT-ε）转录、Sε染色质可及性、转录因子相互作用和同种型转换效率。使用B细胞特异性条件性敲除小鼠品系进行体内实验测试。分析过敏性鼻炎患者和匹配健康志愿者的鼻下鼻甲活检组织，进行相关性免疫分析。评估了针对该双信号轴不同节点的三种药理学干预措施。
结果： 在固定CD40L共刺激下，孤立的BCR或孤立的IL-4Rα刺激支持IgG4/IgA转换，但在小鼠和人初始B细胞中产生的GLT-ε转录极少、Sε区域染色质关闭，功能性IgE分泌可忽略不计。两条通路的同时激活触发了NF-κB和STAT6在Sε位点的物理相互作用和基因组共占据，招募CBP/p300沉积允许性组蛋白修饰、重塑染色质并使AID能够充分加载以支持IgE CSR。在人鼻黏膜中，过敏性鼻炎患者B细胞NF-κB-STAT6活性协同与局部IgE升高相关，而在健康对照组织中观察到信号解偶联。在我们的检测系统中，药理学靶向IL-4Rα、循环游离IgE或NF-κB-STAT6蛋白-蛋白界面可减少IgE产生，而不影响IgG/IgA生成。
结论： 我们的实验数据在测试的体外和临床前小鼠系统中支持IgE CSR的协同门控模型。在这些实验设置下，同时发生的BCR-NF-κB和IL-4Rα-STAT6通路输入似乎强烈需要以实现稳健的有效IgE重排。这一信号协同框架为限制IgE反应的生理约束提供了机制性见解。这些观察是否能转化为临床效用值得进一步独立研究。

英文摘要

BACKGROUND: Aberrant immunoglobulin E (IgE) class-switch recombination (CSR) underlies globally prevalent type 2 allergic disorders affecting hundreds of millions of people worldwide. Under homeostatic conditions, IgE production is tightly restrained, whereas IgG4 and IgA CSR readily proceed; the molecular mechanisms enforcing this restriction remain incompletely defined. Both BCR-NF-κB and IL-4Rα-STAT6 contribute to IgE-related transcriptional programming, yet it remains unclear whether isolated or concurrent pathway activity drives functional IgE CSR.
OBJECTIVE: To characterize the molecular threshold for productive IgE CSR under defined experimental conditions and test a signaling-coincidence model, together with exploring potential correlative clinical observations and pre-clinical therapeutic opportunities.
METHODS: Primary naive mouse B cells and human peripheral-blood-derived naive B cells were cultured under constant CD40L co-stimulation with three experimental conditions: isolated BCR activation, isolated IL-4Rα activation, or dual-pathway co-activation. Assays included qPCR, ATAC-seq, ChIP-qPCR, proximity ligation assay (PLA), sequential re-ChIP and flow cytometry to quantify germline ε (GLT-ε) transcription, Sε chromatin accessibility, transcription-factor interactions and isotype-switching efficiency. B-cell-specific conditional-knockout mouse lines were used for in-vivo experimental testing. Nasal inferior-turbinate biopsies from patients with allergic rhinitis and matched healthy volunteers were analyzed for correlative immune profiling. Three pharmacological interventions targeting distinct nodes of this dual-signal axis were assessed.
RESULTS: Under fixed CD40L co-stimulation, isolated BCR or isolated IL-4Rα stimulation supported IgG4/IgA switching but yielded minimal GLT-ε transcription, closed Sε-region chromatin and negligible functional IgE secretion in mouse and human naive B cells. Concurrent activation of both pathways triggered physical interaction and genomic co-occupancy of NF-κB and STAT6 at the Sε locus, recruiting CBP/p300 to deposit permissive histone modifications, remodeling chromatin and enabling robust AID loading to support IgE CSR. In human nasal mucosa, coincident B-cell NF-κB-STAT6 activity correlated with elevated local IgE among allergic rhinitis patients, whereas signal decoupling was observed in healthy control tissue. Pharmacological targeting of IL-4Rα, circulating free IgE or the NF-κB-STAT6 protein-protein interface reduced IgE production without abrogating IgG/IgA generation within our assay systems.
CONCLUSION: Our experimental data support a coincidence-gated model for IgE CSR in the tested in-vitro and pre-clinical mouse systems. Concurrent BCR-NF-κB and IL-4Rα-STAT6 pathway inputs appear strongly required for robust productive IgE rearrangement under these experimental settings. This signaling-coincidence framework offers mechanistic insights into physiological constraints limiting IgE responses. Whether these observations translate into clinical utility warrants further independent investigation.