Bekeredjian-Ding Isabelle, Doster Anne, Schiller Martin, Heyder Petra, Lorenz Hanns-Martin, Schraven Burkhart, Bommhardt Ursula, Heeg Klaus
Department of Medical Microbiology and Hygiene, University Hospital Heidelberg, Heidelberg, Germany.
J Immunol. 2008 Dec 15;181(12):8267-77. doi: 10.4049/jimmunol.181.12.8267.
In the past, ZAP70 was considered a T cell-specific kinase, and its aberrant expression in B-CLL cells was interpreted as a sign of malignant transformation and dedifferentiation. It was only recently that ZAP70 was detected in normal human B cells. In this study, we show that TLR9-activated B cells resemble B-cell chronic lymphocytic leukemia cells with regard to CD5, CD23, CD25, and heat shock protein 90 expression. Furthermore, stimulatory CpG and GpC DNA oligonucleotides target CD27(+)IgM(+) and CD27(-)IgM(+) B cells (but not IgM(-) B cells) and enhance ZAP70 expression predominantly in the IgM(+)CD27(+) B cell subset. ZAP70 is induced via activation of TLR-7 or -9 in a MyD88-dependent manner, depends on protein kinase B (PKB)/mammalian target of rapamycin signaling and is rapamycin sensitive. Furthermore, ZAP70 expression levels correlate with induction of cyclin A2, prolonged B cell proliferation, and sustained induction of PKB. These events are not observed upon CD40 ligation. However, this deficit can be overcome by the expression of constitutively active PKB, given that CD40 ligation of PKB-transgenic B cells induces B cell proliferation and ZAP70 expression. These results highlight a major difference between CD40- and TLR-7/9-mediated B cell activation and suggest that ZAP70 expression levels in B cells give an estimate of the proliferative potential and the associated PKB availability.
过去，ZAP70被认为是一种T细胞特异性激酶，其在B细胞慢性淋巴细胞白血病（B-CLL）细胞中的异常表达被解释为恶性转化和去分化的标志。直到最近才在正常人B细胞中检测到ZAP70。在本研究中，我们发现Toll样受体9（TLR9）激活的B细胞在CD5、CD23、CD25和热休克蛋白90表达方面类似于B细胞慢性淋巴细胞白血病细胞。此外，刺激性的CpG和GpC DNA寡核苷酸靶向CD₂₇⁺IgM⁺和CD₂₇⁻IgM⁺ B细胞（而非IgM⁻ B细胞），并主要在IgM⁺CD₂₇⁺ B细胞亚群中增强ZAP70表达。ZAP70通过MyD88依赖的方式经TLR-7或-9激活而诱导产生，依赖于蛋白激酶B（PKB）/雷帕霉素哺乳动物靶标信号传导，且对雷帕霉素敏感。此外，ZAP70表达水平与细胞周期蛋白A2的诱导、B细胞增殖延长以及PKB的持续诱导相关。在CD40连接时未观察到这些事件。然而，鉴于PKB转基因B细胞的CD40连接可诱导B细胞增殖和ZAP70表达，通过组成型活性PKB的表达可克服这一缺陷。这些结果突出了CD40和TLR-7/9介导的B细胞激活之间的主要差异，并表明B细胞中ZAP70的表达水平可评估其增殖潜力和相关的PKB可用性。
