CD28的表达在乙型肝炎病毒感染免疫耐受机制中的作用

目的探讨乙肝病毒携带者外周血T淋巴细胞上的CD28表达在乙肝病毒感染免疫耐受机制中的作用以及影响其CD28表达的可能因素.方法选择其血清中HBsAg、HBeAg、抗HBc-IgM和HBVDN均为阳性的乙肝病毒携带者(肝功能正常)35例;正常对照组11例以及急性乙型肝炎患者5例.分别采用流式细胞学、细胞RNA提取和RT-PCR等技术,检测实验对象外周血单核细胞上的CD4、CD8、CD28和CD25等蛋白分子的表达情况,CD28 mRNA的含量以及外周血单核细胞中HBVDNA的存在情况.结果(1)乙肝病毒携带者外周血T淋巴细胞(CD4和CD8 T淋巴细胞)上CD28的表达低下,尤以CD8 T淋巴细胞更为明显(CD25/CD4为14.42%,CD28/CD8为7.39%);而正常对照组(CD28/CD4为24.57%,CD28/CD8为29.54%)和急性乙型肝炎组(CD28/CD4为26.25%,CD28/CD8为18.42%)则均有较高的表达.其与乙肝病毒携带者的结果相比较,有着显著或非常显著之差异(P＜0.05,P＜0.01).同时,通常用于表示T淋巴细胞激活状态的CD25在乙肝病毒携带者的外周血T淋巴细胞上的表达也低下(CD25/CD4为9.10%,CD25/CD8为7.93%),特别是以CD8T淋巴细胞上的表达低下尤为明显.其与正常对照组的相应结果(CD25/CD4为4.2%,CD25/CD8为1.48%)相比较,差异显著或极为显著(P＜0.05,P＜0.01).(2)乙肝病毒携带者外周血单核细胞内CD28 mRNA的水平也较正常对照组的更低.(3)乙肝病毒携带者外周血单核细胞中HBVDNA的检出率(60.0%)明显高于正常对照组(0%),两者相比差异极为显著(P＜0.01).结论乙型肝炎病毒持续感染者的外周血中T淋巴细胞,尤其足CD8 T细胞上的激活受体CD28表达水平较正常人明显降低,其细胞中CD28 mRNA水平也降低,均可能造成T淋巴细胞激活所必需的第二信号产生减少,使T淋巴细胞的激活受影响,导致机体细胞免疫功能降低.从而诱导机体对乙型肝炎病毒感染免疫耐受的产生.造成乙肝病毒感染持续存在,迁延不愈.而HBV对T淋巴细胞的感染可能是造成其细胞上CD28表达水平低下的原因之一.

The Effect of the Expression of CD28 in Immuno-tolerance of Hepatitis Bvirus Infection

Purpose To probe the effect of expression of CD28 on peripheral T lymphocyts in immune-tolerance of hepatitis B virus (HBV)infection and the factors that affect CD28 expression. Methods The expression of CD4,CD8,CD28 and CD25 on peripheral mononuclear cells (PMCs) were detected in 35 cases of HBV carriers,which were HBsAg, HBeAg,anti -HBc -IgM and HBVDNA positive in their sera; 11 cases of normal control and 5cases of acute hepatitis B by Flow Cytomery Analysis.Si-multaneously,eth level of CD28, mRNA and HBVDNA in their PMCs of above cases were detected by RT-PCR. Results (l)The expression of CD28 on the peripheral T cells (CD4 and CD8 T cells),espe-cially that on CD8 T cells was much lower than that in normal control and acute hepatitis B. (P< 0.05 ,P<0.01).The expression of CD25,which indicated the activation state of T cells,on the peripheral T cells was also much lower in HBV carriers than that in normal control(P<0.05,.P<0.01). (2)The level of CD28 mRNA in PMCs of HBV carriers was weaker than that of normal control and acute hepatitis B. (3)The positive rate of HBV DNA in PMCs of HBV carriers was 60.0% ,which was much higher than that of normal contor (0%) (P<0.01). Conclusion The expression of activating receptor CD28 on the peripheral T lymphoeytes,especially on CD8 T cells of HBV carriers is much lower than that of normal control and acute hepatitis B,which means that the second signal that is necessary for the activation of T cells is weakened. The activation of T cells in inhibited,which results in that HBV can not be eliminated by the cellular immunity and the immuno-tolerance for HBV infection is induced.Besides,the HBV infection in PMCs may be on of the causes that results in the decrease of CD28 on the peripheral T cells.