The B cell response to Ehrlichia muris is dominated by plasmablasts (PBs), with few-if any-germinal centers (GCs), yet it generates protective immunoglobulin M (IgM) memory B cells (MBCs) that express the transcription factor T-bet and harbor V-region mutations. Because Ehrlichia prominently infects the liver, we investigated the nature of liver B cell response and that of the spleen. B cells within infected livers proliferated and underwent somatic hypermutation (SHM). Vh-region sequencing revealed trafficking of clones between the spleen and liver and often subsequent local clonal expansion and intraparenchymal localization of T-bet+ MBCs. T-bet+ MBCs expressed MBC subset markers CD80 and PD-L2. Many T-bet+ MBCs lacked CD11b or CD11c expression but had marginal zone (MZ) B cell phenotypes and colonized the splenic MZ, revealing T-bet+ MBC plasticity. Hence, liver and spleen are generative sites of B cell responses, and they include V-region mutation and result in liver MBC localization.

中文翻译：

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肝脏是B细胞对毛虫埃里希氏菌反应的生殖部位。

B细胞对毛虫衣原体的反应主要由浆母细胞（PBs）主导，几乎没有任何萌发中心（GC），但它会产生保护性免疫球蛋白M（IgM）记忆B细胞（MBC），表达转录因子T-bet并带有V区突变。由于埃希氏菌主要感染肝脏，因此我们研究了肝B细胞反应和脾脏的本质。感染的肝脏中的B细胞增殖并经历体细胞超突变（SHM）。Vh区域测序揭示了脾脏和肝脏之间的克隆运输，并经常随后出现T-bet + MBC的局部克隆扩增和实质内定位。T-bet + MBC表达了MBC子集标记CD80和PD-L2。许多T-bet + MBC缺乏CD11b或CD11c表达，但具有边缘区（MZ）B细胞表型，并在脾脏MZ上定殖，显示T-bet + MBC可塑性。因此，肝脏和脾脏是B细胞反应的发生部位，它们包括V区突变并导致肝脏MBC定位。