Laboratory of Cellular Therapy, Department of Hematology and Oncology, Children's University Hospital, Friedrich-Alexander-Universität Erlangen-Nürnberg, Klinikum Erlangen, Erlangen 91054, Germany.
J Immunol. 2012 May 15;188(10):4810-8. doi: 10.4049/jimmunol.1101610. Epub 2012 Apr 13.
The life span of dendritic cells (DCs) is determined by the balance of pro- and antiapoptotic proteins. In this study, we report that serum-free cultured human monocyte-derived DCs after TLR stimulation with polyinosinic acid-polycytidylic acid or LPS underwent apoptosis, which was correlated with low TNF production. Apoptosis was prevented by the addition of exogenous TNF or by concomitant stimulation with R-848, which strongly amplified endogenous TNF production. Neutralization of TNF confirmed that DC survival was mediated by autocrine TNF induced either by stimulation with R-848 or by ligation of CD40. DCs stimulated by polyinosinic acid-polycytidylic acid or IFN-β, another known inducer of DC apoptosis, were characterized by high levels and activation of the proapoptotic protein BAK. The ratio of antiapoptotic BCL-2 to BAK correlated best with the survival of activated DCs. Addition of TNF increased this ratio but had little effect on BAX and XIAP. Knockdown experiments using small interfering RNAs confirmed that the survival of activated and also of immature DCs was regulated by BAK and showed that TNF was protective only in the presence of FLIP(L). Together, our data demonstrate that the survival of DCs during differentiation and activation depends on autocrine TNF and that the inhibition of BAK plays an important role in this process.
树突状细胞 (DC) 的寿命取决于促凋亡和抗凋亡蛋白之间的平衡。在这项研究中，我们报告说，经多聚肌苷酸-多聚胞苷酸或 LPS 刺激的无血清培养的人单核细胞来源的 DC 会发生凋亡，这与 TNF 产生减少有关。添加外源性 TNF 或同时用 R-848 刺激可预防凋亡，R-848 强烈放大内源性 TNF 产生。TNF 的中和证实，DC 的存活是由 R-848 刺激或 CD40 交联诱导的自分泌 TNF 介导的。多聚肌苷酸-多聚胞苷酸或 IFN-β刺激的 DC，另一种已知的 DC 凋亡诱导剂，其特征是高水平和促凋亡蛋白 BAK 的激活。抗凋亡蛋白 BCL-2 与 BAK 的比值与活化 DC 的存活相关性最好。添加 TNF 增加了该比值，但对 BAX 和 XIAP 影响很小。使用小干扰 RNA 的敲低实验证实，活化和未成熟 DC 的存活受 BAK 调节，并且 TNF 仅在存在 FLIP(L)时才具有保护作用。总之，我们的数据表明，DC 在分化和激活过程中的存活取决于自分泌的 TNF，并且 BAK 的抑制在这个过程中起着重要作用。
