Germinal centers (GCs) are sites wherein B cells proliferate and mutate their immunoglobulins in the dark zone (DZ), followed by affinity-based selection in the light zone (LZ). Here, we mapped the location of single B cells in the context of intact lymph nodes (LNs) throughout the GC response, and examined the role of BCR affinity in dictating their position. Imaging of entire GC structures and proximal single cells by light-sheet fluorescence microscopy revealed that individual B cells that previously expressed AID are located within the LN cortex, in an area close to the GC LZ. Using in situ photoactivation, we demonstrated that B cells migrate from the LZ toward the GC outskirts, while DZ B cells are confined to the GC. B cells expressing very-low-affinity BCRs formed GCs but were unable to efficiently disperse within the follicles. Our findings reveal that BCR affinity regulates B cell positioning during the GC response.

中文翻译：

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全器官成像揭示的生发中心反应过程中的 B 细胞传播模式。

生发中心 (GC) 是 B 细胞在暗区 (DZ) 中增殖和突变其免疫球蛋白的位点，然后在亮区 (LZ) 中进行基于亲和力的选择。在这里，我们在整个 GC 反应中绘制了完整淋巴结 (LN) 环境中单个 B 细胞的位置，并检查了 BCR 亲和力在决定其位置方面的作用。通过光片荧光显微镜对整个 GC 结构和近端单细胞进行成像显示，先前表达 AID 的单个 B 细胞位于 LN 皮层内，靠近 GC LZ 的区域。使用原位光活化，我们证明 B 细胞从 LZ 迁移到 GC 郊区，而 DZ B 细胞仅限于 GC。表达极低亲和力 BCR 的 B 细胞形成 GC，但无法有效地分散在毛囊内。