Robinson Marcus James, Tarlinton David Mathew
Department of Immunology, Monash University, Level 6 89 Commercial Road, Prahran VIC 3004.
Department of Immunology, Monash University, Level 6 89 Commercial Road, Prahran VIC 3004.
Immunol Lett. 2025 Jun;273:106980. doi: 10.1016/j.imlet.2025.106980. Epub 2025 Feb 7.
Antibodies of the IgE and IgG1 isotypes are relevant for type 2 immunity. In vivo, the production of both is elevated by IL-4, but differentially affected by IL-21, with IgE suppressed and IgG1 production enhanced by IL-21. However, whether the cytokines drive these outcomes primarily by impacting antibody-secreting, proliferating plasmablasts (PB), or their germinal center B cell precursors, is challenging to unravel. In vitro analyses using Nojima cultures, wherein naïve B cells are activated on fibroblasts co-expressing CD40L and BAFF, allows for evaluation of this problem. Here, we explore how IL-4 and IL-21 alone and in combination affect Nojima-cultured B cell proliferation and fate, asking what is unique or redundant about exposure to each. In secondary culture, as expected, IL-21 amplified replicative expansion. IL-21 also selectively promoted the differentiation of IgG1 B cells into PB. The effect was countermanded by synchronous exposure to IL-4, suggesting competing signaling pathways are triggered by the two cytokines independently. Secondary culture with IL-4 alone promoted IgE B cell genesis without increasing replicative expansion. Combined exposure to IL-21 and IL-4 led to increased IgE class-switching and proliferative expansion, suggesting that once B cells are switched to IgE, IL-21 can promote IgE+ B cell proliferation. Thus, in culture IL-21 operates to promote proliferation and also drives differentiation of IgG1+ B cells into PB whereas IL-4 has an ongoing role in IgE B cell genesis. The balance of IL-4 and IL-21 thus impacts the fate of in vitro-generated germinal center B cells and highlights how the notable IgE-suppressing effects of IL-21 in vivo likely precede the class-switch step, after which IL-21 may amplify IgE production by virtue of its pro-proliferative effects.
IgE和IgG1同种型抗体与2型免疫相关。在体内，这两种抗体的产生均由IL-4升高，但受IL-21的影响不同，IL-21抑制IgE并增强IgG1的产生。然而，细胞因子主要是通过影响分泌抗体、增殖的浆母细胞（PB）还是其生发中心B细胞前体来驱动这些结果，这很难弄清楚。使用野岛培养物进行的体外分析，即幼稚B细胞在共表达CD40L和BAFF的成纤维细胞上被激活，可以评估这个问题。在这里，我们探讨单独和联合使用IL-4和IL-21如何影响野岛培养的B细胞增殖和命运，询问每种暴露的独特之处或冗余之处。在二次培养中，正如预期的那样，IL-21放大了复制性扩增。IL-21还选择性地促进IgG1 B细胞分化为PB。同步暴露于IL-4可抵消这种作用，表明这两种细胞因子独立触发了相互竞争的信号通路。单独用IL-4进行二次培养可促进IgE B细胞生成而不增加复制性扩增。联合暴露于IL-21和IL-4导致IgE类别转换和增殖性扩增增加，表明一旦B细胞转换为IgE，IL-21可以促进IgE+B细胞增殖。因此，在培养中，IL-21起促进增殖的作用，并驱动IgG1+B细胞分化为PB，而IL-4在IgE B细胞生成中持续发挥作用。因此，IL-4和IL-21的平衡影响体外产生的生发中心B细胞的命运，并突出了IL-21在体内显著的IgE抑制作用可能在类别转换步骤之前发生，在此之后，IL-21可能因其促增殖作用而放大IgE产生。
