CD28/CTLA-4共刺激分子在再生障碍性贫血免疫发病机制中的作用

目的 研究CD28、CTLA-4在再生障碍性贫血（AA）免疫发病机制中的可能作用。方法 以流式细胞术分别分析23例发病期AA、10例恢复期AA患者和15名正常人骨髓细胞中CD3^＋CD4^＋T细胞上CD28、CTLA-4表达率，Th1、Th2细胞比例，评价CD28、CTLA4表达与Th1／Th2、中性粒细胞绝对值（ANC）之间的关系。结果 ①正常对照组CD3^＋CD4^＋T细胞上CD28、cTLA4表达率及CD28^＋／CTLA-4^＋比值分别为（31．40±10．83）％、（2．45±1．30）％、17．02±13．44，AA患者发病期分别为（39．84±10．89）％、（1．43±0．67）％、43．04±37．61，AA患者恢复期分别为（22．00±9．08）％、（3．46±2．26）％、10．49±7．80；与正常对照组比较，AA患者发病期CD28显著升高（P〈0．05），CTLA-4显著下降（P=〈0．01），CD28^＋／CTLA4^＋比值相应地亦显著升高（P〈0．05），而恢复期上述数值与正常对照组比较，差异无统计学意义（P〉0．05）。②正常对照组Th1、Th2细胞、Th1／Th2比值分别为（4．21±2．11）％、（1．99±1．27）％、2．46±1．28，AA发病期为（11．13±4．96）％、（2．46±1．65）％、5．20±1．98，恢复期分别为（5．39±4．29）％、（2．53±2．41）％、2．87±1．43；与正常对照组比较，AA发病期Th1增高，Th1、Th2平衡向Thl偏移（P值均〈0．01），恢复期与正常对照组比较，差异无统计学意义。③AA患者CD28^＋／cTLA4^＋比值与Thl／Th2比值呈正相关（P〈0．05），ANC与CD3^＋CD4^＋CD28^＋T细胞数呈负相关（P〈0．01），与CD3^＋CD4^＋CTLA-4^＋T细胞数呈正相关（P〈0．01）。结论 ①AA发病期患者骨髓CD4^＋T细胞表面共刺激分子表达异常，CD28升高，而CTLA-4下降，AA患者骨髓T细胞处于“预激活”状态；②CD28／CTLA-4比值与Th1／T12．比值呈正相关提示：CD28、CTLA-4表达失衡可引起Th细胞格局偏移，Th1型细胞增多。③ANC和CD28、CTLA-4间相关分析进一步说明CD28、CTLA-4与AA的发生、发展有关。

Role of CD28/CTLA-4 costimulators in immune pathophysiology of aplastic anemia

OBJECTIVE: To explore the possible role of CD28/CTLA-4 costimulators in immune pathophysiology of acquired aplastic anemia(AA). METHODS: By FACS, the percentages of CD28, CTLA-4 expressing CD3+ CD4+ T cells and the level of Th1, Th2 in bone marrow were detected in 23 AA patients at active phase, 10 at recovery phase and 15 normal controls. The relationship between the costimulators, Th1, Th2, and absolute neutrophil counts (ANC) was evaluated. RESULTS: (1) The percentage of CD28 and CTLA-4 expressing CD3+ CD4+ T cells in bone marrow, and CD28+/CTLA-4+ ratios were (31.40 +/- 10.83)%, (2.45 +/- 1.30)% , and 17.02 +/- 13.44 in normal controls respectively, (39.84 +/- 10.89)%, (1.43 +/- 0.67)%, and 43.04 +/- 37.61 in AA at active phase, respectively, (22 +/- 9.08)%, (3.46 +/- 2.26)%, and 10.49 +/- 7.8 in AA at recovery phase, respectively. The percentage of CD28 and CD28+/CTLA-4+ ratio were significantly higher, while CTLA-4 were lower in active phase AA patients than in normal controls (P < 0.05). These values in recovery phase AA were comparable to those in normal controls. (The Th1, Th2, and Th1/Th2 in bone marrow were (4.21 +/- 2.11)%, (1.99 +/- 1.27)%, and 2.46 +/- 1.28 in normal controls respectively, (11.13 +/- 4. 96)%, (2.46 +/- 1.65)%, and 5.20 +/- 1.98 in active phase AA and (5.39 +/- 4.2)9%, (2.53 +/- 2.41)%, and 2.87 +/- 1.43 in recovery phase AA, respectively. The percentage of Th1 and Th1/Th2 ratio were significantly higher in AA patients at active phase than in normal controls (P < 0.05). (3) The CD28+/CTLA-4+ ratio was positively related to the Th1+ /Th2+ ratio (P < 0.05). ANC was negatively related to CD3+ CD4+ CD28+ T cells (P < 0.01), and positively to CD3 + CD4 ' CTLA-4' T cells (P < 0.01) respectively. CONCLUSION: (1) The expression of CD28 was increased while CTLA-4 decreased on the membranes of CD3+ CD4+ T cells in bone marrow of AA patients. (2) The abnormal expression of CD28 costimulator promoted the shift of immune balance to Thl type. (3) The unbalance of CD28+ / CTLA-4+ is important for the immune pathophysiology of AA.