Stable, long-term culture of primary B lymphocytes has many potential scientific and medical applications, but remains an elusive feat. A major obstacle to long-term culture is that in vitro mitogens quickly drive B cells to differentiate into short-lived plasma cells (PCs). PC differentiation is governed by opposing teams of transcription factors: Pax5, Bach2, and Bcl6 suppress PC commitment, whereas IFN regulatory factor 4 and Blimp1 promote it. To determine whether transcriptional programming could prolong B cell culture by blocking PC commitment, we generated mouse primary B cells harboring gain- or loss-of-function in the key transcription factors, continuously stimulated these cells with CD154 and IL-21, and determined growth potential and phenotypes in vitro. We found that transgenic expression of Bach2 prohibits PC commitment and endows B cells with extraordinary growth potential in response to external proliferation and survival cues. Long-term Bach2-transgenic B cell lines have genetically stable BCRs [i.e., do not acquire V(D)J mutations], express high levels of MHC class II and molecules for costimulation of T cells, and transduce intracellular signals when incubated with BCR ligands. Silencing the Bach2 transgene in an established transgenic cell line causes the cells to secrete large quantities of Ig. This system has potential applications in mAb production, BCR signaling studies, Ag presentation to T cells, and ex vivo clonal expansion for adoptive cell transfer. Additionally, our results provide insight into molecular control over activated B cell fate and suggest that forced Bach2 expression in vivo may augment germinal center B cell or memory B cell differentiation at the expense of PC commitment.

原代 B 淋巴细胞的稳定、长期培养具有许多潜在的科学和医学应用，但仍然是一项难以捉摸的壮举。长期培养的一个主要障碍是体外有丝分裂原会迅速驱动 B 细胞分化为短寿命的浆细胞 (PC)。PC 分化由相反的转录因子团队控制：Pax5、Bach2 和 Bcl6 抑制 PC 承诺，而 IFN 调节因子 4 和 Blimp1 促进它。为了确定转录编程是否可以通过阻断 PC 承诺来延长 B 细胞培养，我们生成了在关键转录因子中具有获得或丧失功能的小鼠原代 B 细胞，用 CD154 和 IL-21 持续刺激这些细胞，并确定生长体外的潜力和表型。我们发现 Bach2 的转基因表达阻止了 PC 的承诺，并赋予 B 细胞响应外部增殖和生存线索的非凡生长潜力。长期Bach2转基因 B 细胞系具有遗传稳定的 BCR [即，不会获得 V(D)J 突变]，表达高水平的 MHC II 类和用于共刺激 T 细胞的分子，并在与 BCR 配体孵育时转导细胞内信号。在已建立的转基因细胞系中沉默Bach2转基因会导致细胞分泌大量 Ig。该系统在 mAb 生产、BCR 信号研究、向 T 细胞呈递 Ag 以及过继细胞转移的体外克隆扩增方面具有潜在应用。此外，我们的结果提供了对激活 B 细胞命运的分子控制的深入了解，并表明在体内强制 Bach2 表达可能会以 PC 承诺为代价增加生发中心 B 细胞或记忆 B 细胞分化。