再生障碍性贫血患者CD4^＋CD25^＋CD127^low调节性T细胞及Notch1表达水平的变化

Significance of CD4^＋CD25^＋CD127^low regulatory T cells and Notch1 pathway in the pathogenesis of aplastic anemia

目的测定再生障碍性贫血（AA）患者治疗前后外周血CD4^＋CD25^＋CD127^low调节性T细胞（Treg）的数量及叉头翼状螺旋转录因子（FOXP3）mRNA、Notch1 mRNA的表达水平，探讨Treg在AA发病中的作用及其机制。方法流式细胞术检测29例初发AA患者、14例环孢素（CsA）治疗后恢复期及11例治疗后未恢复期患者外周血中CD4^＋CD25^＋CD127^lowT细胞、CD4^＋CD25^T细胞的数量，并与正常对照比较；采用RT-PCR检测FOXP3 mRNA和Notch1 mRNA的表达水平，分析两者相关性。结果AA初发组及治疗后未恢复组患者外周血中活化CD4^＋CD25^T细胞占CD4^＋T细胞比例分别为（4．3±0．7）％、（4．2±0．6）％，明显高于正常对照组[（2．4±0．8）％]（P〈0．05）。CsA治疗后恢复组患者比例下降为（2．6±0．7）％（P〈0．05），与对照组比较差异无统计学意义。AA初发组及未恢复组CD4^＋CD25^＋CD127^lowT细胞在CD4^＋T细胞中的比例分别为（2．4±1．2）％、（2．5±1．1）％，较正常对照组[（7．1±2．7）％]及恢复组[（5．3±1．0）％]明显降低（P值均〈0．01）；但后两组比较差异无统计学意义。AA初发组患者FOXP3 mRNA及Notch1 mRNA分别为（0．260±0．011）和（0．018±0．005），较正常对照[（1．307±0．011）和（0．308±0．028）]表达明显下调（P值均〈0．01），治疗后分别为（1．287±0．012）和（0．281±0．013），表达较初发组显著提高（P值均〈0．01），与对照组比较差异无统计学意义（P值均〉0．05）。AA患者CD4^＋CD25^＋CD127^lowT细胞、FOXP3均与Notch1表达呈正相关性（P值均〈0．01）。结论AA患者外周血CD4^＋CD25^＋CD127^lowTreg减少，其抑制作用减弱，导致自身反应性T细胞过度活化，抑制造血。其作用机制之一可能与靶细胞表面Notch1分子表达降低相关。

Objective To quantify the CD4^＋CD25^＋CD127^low regulatory T cell （Treg）, the expression levels of forkhead/winged helix transcription factor FOXP3 and Notch1 mRNA in aplastic anemia （AA） patients before and after treatment, and explore the significance of Treg in pathogenesis of AA. Method CD4^＋CD25^＋ and CD4^＋CD25^＋CD127^lowT cells in peripheral blood were examined with FACS in 29 AA patients at active phase, 14 at recovery phase, 11 at unrecovery phase, and 15 normal controls. The levels of FOXP3 mRNA and Notch1 mRNA expression were detected with RT-PCR, and the correlations between Treg, FOXP3 mRNA and Notch1 mRNA were analyzed. Results The percentages of peripheral activated CD4^＋CD25^ T cells in AA patients at active phase （4.3 ± 0.7 ） % and unrecovery phase （4.2 ± 0.6） % were significantly higher than those in normal controls （2.4 ± 0.8） % （P 〈 0.05）. The proportion of these cells in AA patients at recovery phase was reduced to （2.6 ± 0.7） % （P 〈 0.05 ）, being no difference from that in control group. The number of CD4^＋CD25^＋CD127^lowT cells in AA patients at active phase （2.4 ± 1.2）% and unrecovery phase （2.5 ± 1. 1 ）% was decreased significantly compared with those in normal controls （7.1 ±2.7）% （P〈0.01） and in AA patients at recovery phase （5.3 ±1.0）% （P〈0.01） , there was no difference between the latter two groups. In active phase AA patients, the levels of FOXP3 mRNA and Notch1 mRNA （0.260 ± 0.011 and 0.018 ± 0. 005, respectively） were lower than that in control group （ 1. 307 ± 0.011 and 0.308 ± 0.028, respectively） （ P 〈 0.01 and P 〈 0.01 ）. After treatment, the levels significantly increased to 1. 287 ±0.012 and 0.281 ±0.013 （P 〈0.01 and P 〈0.01 ） , but there was no difference with that of normal controls （P 〉 0.05 ）.CD4^＋CD25^＋CD127^lowT cells and FOXP3 were positively related with Notch1 （P 〈0.01） in AA patients. Conclusion The decreased number and suppressive activity of CD4^＋CD25^＋CD127^low Treg cells in the peripheral blood of AA patients cause over-activation of autoreactive T cells and suppression of haematopoiesis. One of the mechanisms maybe the reduced expression of Notch1 in the target cells.