Molecular control of germinal center selection and affinity maturation

项目概要/摘要 生殖中心（GC）是抗体体细胞超突变（SHM）和亲和力成熟的位点， 因此对于针对病原体的有效体液免疫应答至关重要。GC中的有效亲和力成熟 需要B细胞在两种不同的细胞状态之间循环，与不同的微畸形相关。 （i）“增殖”模式，当B细胞分裂并经历SHM时，其在黑暗中发生 区域（DZ）;和（ii）“选择”模式，当突变的B细胞基于它们的 对抗原的亲和力，这发生在GC轻区（LZ）。虽然我们之前的工作定义了 与LZ和DZ状态广泛相关的转录程序，我们对细胞如何决定 当一个状态和另一个状态之间的转换未完成时。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 细胞可以进一步被解析成与不同阶段相关的另外的转录上不同的状态， GC选择。在这里，我们建议将同步GC选择的体内模型与新的小鼠模型联合收割机结合， 遗传模型，信号传导抑制剂治疗，单细胞mRNA测序，以确定完整的 GC转录状态的互补并解决这些状态如何与GC选择相关。一 这些程序的清晰定义将提高我们对GC B细胞选择和亲和力的理解 成熟是受控的，对疫苗设计有影响。此外，确定GC B细胞 增殖受到控制将进一步加深我们对GC衍生的B细胞淋巴瘤的理解，这些淋巴瘤依赖于类似的 作为GC实现持续增殖的机制。

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.