Jiangsu Province Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing 210046, PR China.
Cytokine. 2011 Feb;53(2):215-22. doi: 10.1016/j.cyto.2010.11.006. Epub 2010 Dec 8.
B cell activating factor belonging to the TNF family (BAFF, also called BLyS, TALL-1, THANK, or zTNF4) is an important survival factor for B cells, and is able to regulate T-cell activation. Recently, we have demonstrated that treatment of mice with human soluble BAFF (hsBAFF) causes a significant increase of percentages of splenic CD4(+) T lymphocytes dose-dependently, but the CD8(+) T lymphocyte percentages maintained unchanged. Here, we show that hsBAFF significantly enhanced CD4(+) T lymphocyte response of cultured mouse splenic cells, and hsBAFF induced the proliferation and IL-2/IFN-γ secretion of purified CD4(+) T lymphocytes suboptimally stimulated through anti-CD3. Of importance, we observed that IL-2 or IFN-γ cytokine has additive effect on the proliferation and activity of hsBAFF-stimulated CD4(+) T lymphocytes. Using Flow cytometry with fluorescent probe, Fluo-3/AM, we found that hsBAFF elicited Ca(2+) elevation contributing to CD4(+) T cell proliferation. This is evidenced by our finding that pretreatment with BAPTA/AM, an intracellular Ca(2+) chelator, significantly attenuated the proliferation of hsBAFF-stimulated CD4(+) T lymphocytes. Subsequently, we revealed that hsBAFF-stimulated CD4(+) T cell proliferation was markedly suppressed after pretreatment with EGTA, an extracellular Ca(2+) chelator, or with 2-APB, an inhibitor of Ca(2+) influx through CRAC channels, respectively, suggesting that extracellular Ca(2+) influx due to hsBAFF is closely associated with Ca(2+) elevation contributing to CD4(+) T cell proliferation. In addition, we noticed that hsBAFF-treated cells conferred partial resistance to decrease of cellular viability induced by thapsigargin (Tg), an endoplasmic reticulum (ER) Ca(2+)-ATPase inhibitor. Taken together, our data indicate that hsBAFF may promote CD4(+) T cell proliferation and response by upregulation of Ca(2+) homeostasis.
B 细胞激活因子属于 TNF 家族（BAFF，也称为 BLyS、TALL-1、THANK 或 zTNF4）是 B 细胞的重要存活因子，能够调节 T 细胞的激活。最近，我们已经证明，用人类可溶性 BAFF（hsBAFF）治疗小鼠会导致脾 CD4(+)T 淋巴细胞的百分比显著增加，呈剂量依赖性，但 CD8(+)T 淋巴细胞的百分比保持不变。在这里，我们表明 hsBAFF 显著增强了培养的小鼠脾细胞中 CD4(+)T 淋巴细胞的反应，hsBAFF 诱导了通过抗 CD3 亚最佳刺激的纯化 CD4(+)T 淋巴细胞的增殖和 IL-2/IFN-γ 分泌。重要的是，我们观察到 IL-2 或 IFN-γ 细胞因子对 hsBAFF 刺激的 CD4(+)T 淋巴细胞的增殖和活性有相加作用。使用带有荧光探针 Fluo-3/AM 的流式细胞术，我们发现 hsBAFF 引起了 Ca(2+) 升高，有助于 CD4(+)T 细胞增殖。这一点得到了我们的发现的证实，即用细胞内 Ca(2+)螯合剂 BAPTA/AM 预处理可显著减弱 hsBAFF 刺激的 CD4(+)T 淋巴细胞的增殖。随后，我们揭示了在用细胞外 Ca(2+)螯合剂 EGTA 或 CRAC 通道 Ca(2+) 内流抑制剂 2-APB 预处理后，hsBAFF 刺激的 CD4(+)T 细胞增殖明显受到抑制，这表明 hsBAFF 诱导的细胞外 Ca(2+) 内流与 Ca(2+) 升高密切相关，有助于 CD4(+)T 细胞增殖。此外，我们注意到 hsBAFF 处理的细胞赋予了对内质网（ER）Ca(2+)-ATP 酶抑制剂 thapsigargin（Tg）诱导的细胞活力降低的部分抗性。总之，我们的数据表明，hsBAFF 可能通过上调 Ca(2+) 稳态来促进 CD4(+)T 细胞的增殖和反应。
