Molecular control of germinal center selection and affinity maturation

项目摘要/摘要 生发中心(GCs)是抗体体细胞高度突变(SHM)和亲和力成熟的部位，是 因此对病原体的有效体液免疫反应至关重要。GC中的高效亲和力成熟 要求B细胞在两种不同的细胞状态之间循环，与不同的微染色体相关 间隔：(I)“增殖”模式，当B细胞分裂并经历SHM，这发生在黑暗中 GC的区域(DZ)；和(Ii)一种“选择”模式，当突变的B细胞基于它们的 与抗原的亲和力，发生在GC光区(LZ)。虽然我们以前的工作定义了 与LZ和DZ状态广泛相关的转录程序，我们对细胞如何决定的理解 何时在一个国家和另一个国家之间过渡仍未完成。例如，我们不理解 触发DZ B细胞停止增殖并返回LZ的信号，我们也不知道LZ和DZ是否 细胞可以被进一步分析成与不同阶段相关的附加转录不同状态 GC选择。在这里，我们建议将体内同步GC选择的模型与新的小鼠相结合 遗传模型、信号抑制剂处理和单细胞mRNA测序以确定完整的 GC转录状态的补充，并解决这些状态如何与GC选择相关。一个 对这些程序的明确定义将提高我们对GC B细胞选择和亲和力的理解 成熟度受到控制，这对疫苗设计有影响。此外，确定GC B细胞如何 增殖受控将加深我们对GC来源的B细胞淋巴瘤的理解，后者依赖于类似的 如全球气候变化机制，以实现可持续扩散。

PROJECT SUMMARY/ABSTRACT Germinal centers (GCs) are site of antibody somatic hypermutation (SHM) and affinity maturation, and are therefore essential for effective humoral immune responses to pathogens. Efficient affinity maturation in GCs requires that B cells cycle between two different cell states, associated with distinct microanacomical compartments: (i) a “proliferation” mode, when B cells divide and undergo SHM, which takes place in the dark zone (DZ) of the GC; and (ii) a “selection” mode, when mutated B cells compete with each other based on their affinity for antigen, which takes place in the GC light zone (LZ). While our previous work defined the transcriptional programs broadly associated with LZ and DZ states, our understanding of how cells decide when to transition between one state and another remains incomplete. For example, we do not understand the signals that trigger DZ B cells to stop proliferating and return to the LZ, nor do we know whether LZ and DZ cells can be further parsed into additional transcriptionally distinct states that associated with different stages of GC selection. Here, we propose to combine in vivo models of synchronized GC selection with novel mouse genetic models, treatment with signaling inhibitors, and single-cell mRNA sequencing to determine the full complement of GC transcriptional states and to address how these states are associated with GC selection. A clear definition of these programs will improve our understanding of how GC B cell selection and affinity maturation are controlled, with implications for vaccine design. Moreover, determining how GC B cell proliferation is controlled will further our understanding of GC-derived B cell lymphomas, which rely on similar mechanisms as GCs to achieve sustained proliferation.