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

研究综述 老年人通常在威胁生命的传染病中死亡的风险更高，他们不会形成高风险的 针对新感染的优质抗体。针对感染的体液免疫依赖于生发中心 (GC)淋巴结B细胞滤泡的分化过程。在GC中，幼稚的B细胞在 对T细胞依赖抗原的反应，并在体细胞上突变为高亲和力抗体分泌细胞，即， 浆细胞。在幼年小鼠中，B细胞在刺激后呈现出不同的细胞命运，只有一小部分 分化为抗体分泌细胞(ASC)。值得注意的是，浆细胞分化受多个 细胞分裂耦合的表观遗传学程序。染色质可及性改变与基因表达和 揭示转录网络的重新编程及其在特定细胞分裂中调节的基因。一个 幼稚B细胞中的基因亚群在没有转录的情况下显示可访问的启动子，并被标记为 组蛋白修饰H3赖氨酸27三甲基化(H3K27me3)，ZEST同源物的多梳状蛋白增强子 2(EZH2)催化的抑制性修饰。这些基因编码细胞分裂和新陈代谢的调节器， 包括必需的浆细胞转录因子Blimp-1。因此，化学抑制EZH2的结果是 增强了浆细胞的形成。一个重要的问题是，随着年龄的增长，B细胞的扩张性减弱 B细胞和GC对抗原的反应部分是由于免疫衰老和滤泡T细胞缺陷所致 辅助小区(TFH)系统。因此，衰老的小鼠不能产生足够的GC来洞察ASC的命运 和GC B细胞的表观基因组重塑，有必要发展一种组织工程模型 老化的淋巴结节。因此，该R01的长期目标是在体外培养一种“老化的B细胞滤泡”类器官 能够诱导小鼠和人类衰老B细胞早期GC编程的技术，并使 研究浆细胞命运和调节B细胞表观基因组以识别可被 抑制以增强老化B细胞的GC反应。R01汇集了一个由多学科专家组成的团队 在GC有机物、疫苗、佐剂和淋巴组织工程(Ankur Singh，Pi，佐治亚理工学院)和GC 免疫学、ASC命运图谱和表观基因组学(Jeremy Boss、Co-I、Emory Medicine)和微环境 空间经济学(Ahmet Coskun，Co-I，佐治亚理工学院)。

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).