Tissue-engineered Aged B Cell Immune Organoid to Study Antibody Secreting Cell Differentiation Trajectory

研究综述 老年人在威胁生命的传染病中往往有较高的死亡风险，他们不会形成高- 对新感染的高质量抗体。抗感染的体液免疫依赖于生殖中心 (GC)在淋巴结的B细胞滤泡中的分化过程。在GC中，幼稚的B细胞迅速增殖， 应答T细胞依赖性抗原并体细胞突变成高亲和力抗体分泌细胞，即， 浆细胞B细胞在年轻小鼠中受到刺激后呈现异质性细胞命运， 分化为抗体分泌细胞（ASC）。值得注意的是，浆细胞分化是由多种细胞因子控制的。 细胞分裂耦合的表观遗传程序染色质可及性变化与基因表达相关， 揭示了转录网络的重编程以及它们在特定细胞分裂中调节的基因。一 幼稚B细胞中的基因亚群在不存在转录的情况下显示可接近的启动子，并由 组蛋白修饰H3赖氨酸27三甲基化（H3 K27 me 3），一种多梳蛋白增强子zeste同系物 2（EZH 2）催化的抑制性修饰。这些基因编码细胞分裂和代谢的调节因子， 包括必需的浆细胞转录因子Blimp-1。因此，EZH 2的化学抑制导致 促进浆细胞的形成一个重要的问题是，随着年龄的增长，B细胞表现出减少的扩增 B细胞和GC反应对抗原的反应部分是由于免疫衰老和缺陷的滤泡T细胞 辅助细胞（TFH）系统。因此，老年小鼠不能产生足够的GC以提供对ASC命运的了解。 和GC B细胞的表观基因组重塑，有必要开发一种组织工程模型， 老年淋巴结因此，该R 01的长期目标是开发离体“老化B细胞滤泡”类器官 能够诱导来自小鼠和人的老化B细胞的早期GC编程并能够 浆细胞命运和B细胞表观基因组调控的研究，以确定可用于 在老化的B细胞中抑制GC反应。R 01汇集了多学科专家团队 在GC类器官、疫苗、佐剂和淋巴组织工程（Ankur Singh，PI，格鲁吉亚技术）和GC 免疫学、ASC命运作图和表观基因组学（Jeremy Boss，Co-I，Emory Medicine）和微环境 空间组学（Ahmet Coskun，Co-I，格鲁吉亚技术）。

RESEARCH SUMMARY Aged individuals, who are often at higher risk of fatality in life-threatening infectious diseases, do not form high- quality antibodies against new infections. Humoral immunity against infections depends on the germinal center (GC) differentiation process in the B cell follicles of lymph nodes. In GCs, naïve B cells rapidly proliferate in response to T cell-dependent antigens and somatically mutate into high-affinity antibody-secreting cells, i.e., plasma cells. B cells assume heterogeneous cell fates upon stimulation in young mice, with only a fraction differentiating into antibody-secreting cells (ASC). Notably, plasma cell differentiation is controlled by multiple cell division-coupled epigenetic programs. Chromatin accessibility changes correlate with gene expression and reveal the reprogramming of transcriptional networks and the genes they regulate at specific cell divisions. A subset of genes in naive B cells display accessible promoters in the absence of transcription and are marked by the histone modification H3 lysine 27 trimethylation (H3K27me3), a Polycomb protein Enhancer of zeste homolog 2 (EZH2) catalyzed repressive modification. Such genes encode regulators of cell division and metabolism and include the essential plasma cell transcription factor Blimp-1. Consequently, chemical inhibition of EZH2 results in enhanced plasma cell formation. A significant concern is that with aging, B cells exhibit a decreased expansion of B cells and GC reaction in response to antigen partly due to immune senescence and a defective follicular T helper cell (TFH) system. As a result, aged mice cannot generate sufficient GCs to provide insight into ASC fate and epigenomic remodeling of GC B cells, necessitating the development of a tissue-engineered model of an aged lymph node. Therefore, the long term goal of this R01 is to develop an ex vivo “aged B cell follicle” organoid technology capable of inducing early GC programming of aged B cells from both mice and humans and enabling the study of plasma cell fate and regulation of the epigenome of B cells to identify checkpoint targets that can be suppressed to boost GC response in aged B cells. The R01 brings together a multidisciplinary team of experts in GC organoids, vaccine, adjuvants, and lymphoid tissue engineering (Ankur Singh, PI, Georgia Tech) and GC immunology, ASC fate mapping and epigenomics (Jeremy Boss, Co-I, Emory Medicine), and microenvironment spatial omics (Ahmet Coskun, Co-I, Georgia Tech).