中国科学院机构知识库网格
Chinese Academy of Sciences Institutional Repositories Grid
调节性T细胞在SIVmac239感染中国恒河猴中的变化及其机制的初步研究

文献类型:学位论文

作者李少遊
学位类别博士
答辩日期2009-07
授予单位中国科学院研究生院
授予地点北京
导师郑永唐
关键词SIVmac239 调节性T细胞 动物模型
其他题名The Variation and its Elementary Mechanism of Regulatory T-Cells in SIVmac239 Infected Chinese Rhesus Macacques
中文摘要CD4+CD25+调节性T细胞是1995年才发现的一个具有免疫抑制功能的T细胞亚群,主要通过细胞与细胞间直接接触和分泌抑制性细胞因子发挥作用,在维持机体免疫自稳、防止自身免疫以及肿瘤免疫、移植免疫等方面起着重要作用。有关Treg HIV/SIV病毒感染及AIDS的进展关系密切,但却有两种不同的观点。一种认为Treg的数量和功能受到损伤,从而导致宿主免疫系统过度活化。另一种则认为Treg在早期抑制了针对HIV/SIV的特异性的免疫反应,从而导致机体无法清除感染的病毒。本文利用动物模型对CD4+CD25+调节性T细胞在SIV感染后的数量和功能做了动态的检测,并对其中的机制做了初步的探讨。 我们首先建立了SIVmac239病毒株对中国起源的恒河猴感染的动物模型,建立了前病毒的检测方法、血浆病毒载量的测定方法、血浆病毒特异性抗体的测定方法,以及病毒的分离方法,并获得了早期感染的相关数据。 在研究中我们发现,SIV感染后的1周后即可在恒河猴外周单个核细胞DNA中检测到前病毒。病毒血症也在1周后出现,并很快达到高峰。不同的个体对病毒感染的体液免疫不尽相同,血浆抗体很快出现,但是99003猴抗体下降很快,而99083猴则保持了一定数量的抗体。同时,伴随SIV的感染进程的还有T淋巴细胞的数量变化,CD4+T细胞数量持续下降,而CD8+T细胞数量则在增加,出现CD4/CD8倒置的现象。以上说明恒河猴被SIV所成功感染。 在该动物模型的基础上,我们利用体内传代的SIVmac239病毒株,对4只健康恒河猴进行了感染,并对CD4+CD25+调节性T细胞(Treg)亚群在数量上的变化进行了检测,并对其中的机制做了初步探讨。 我们在研究中发现,外周血中的Treg在SIV感染后无论是绝对数量还是在占CD4+T细胞中的相对数量均有增加,而且Treg仍然保持了对靶细胞的抑制功能。对腹部淋巴结的分析显示,SIV感染后的一段时期内,该部位FoxP3 mRNA的表达水平也在上升,TGF-β、IL-10的转录也显著增加。前者可以通过抑制树突状细胞间接抑制效应细胞,而后者则是一个抑制性的细胞因子,可以直接作用于靶细胞。因此,我们推测SIV引起免疫系统的过度活化可能不是由于Treg功能的受损,其中的机制需要深入研究。 Treg表达CCR5表面分子(HIV辅助受体之一),同时也有CD4分子的表达,因此推测HIV/SIV可以感染Treg。但是国内外这方面的文献很少。我们对Treg中前病毒的检测发现,SIV可以感染Treg,而且对Treg的感染比例高于CD4+CD25-T细胞。这个结果与Treg绝对数量的上升的结果说明,SIV感染Treg但可能却没有杀伤Treg,因此Treg在数量上有所增加。不过,其中的机制仍有待于进一步的研究。 在对SIV引起的体液免疫的研究中还发现,机体针对SIV不同抗原的抗体有不同的模式。部分抗原很快就产生了比较强的反应,但是却不能维持高水平的表达。而针对p27蛋白的抗体产生比较晚,但却长时间维持在比较高的水平。是否这样高水平的抗体有助于控制病毒复制是个值得探讨的问题。
英文摘要CD4+CD25+ regulatory T-cell (Treg) was found to be a suppressive subset of T-cell, in 1995, by Japanese immunologist Dr. Sakaguchi. Treg inhibits effector T cells by direct contact with its target cells. Or it surpresses target cells by its secreting immuno-suppressive cytokines such as TGF-βor IL-10. Current understanding of Treg’s roles in maintaining the balance between immunity against pathogens and tolerance has been greatly expanded by its double-faced function in immunity against HIV. With its surpressive function, Treg may be disarmed in HIV infection, which results in an overactivated immune system. While some research showes that the quantity of Treg cells has been remarkablely expanded in primary infection. Treg dysfunctions both HIV-specific helper T cells and CTLs. Depleting Treg from CD4+ T cell leads to a reconstitution of strong immunity against HIV. On our established animal model, a SIV-Chinese rhesus macacaque one, we made a study on Treg in SIV-infected rhesus monkeys. One week post infection, proviral DNA in PBMC could be detected by nested-PCR. CD4+ T cells decreased greatly, while CD8+ T cells increased in quantity. And we found SIV-p27 specific antibodies lagged two weeks or so behind some SIV-specific antibodies. However, the latter peaked, quickly after which they dropped even to undetectable level. But p27 antibodies maintained at high level throughout this period. The underlying mechanism remains unknown. And we expect to find out if p27 antibodies will help the hosts to control the replication of SIV more effectively. Both the absolute quantity and the relative quantity of Treg in CD4+ T cells increased dramatically in primary and chronic SIV-infection. Moreover, it seemed that those Tregs had not been negatively affected in its immuno- suppressive abilities in downregulating IFN-γ and IL-2 secretion of CD4+CD25- T cells. CCR5, one of the co-receptor of HIV/SIV infection, is also expressed on the surface of Tregs. So it is presumed that Treg could be targets cell of SIV. But references in this topic could rarely be found in journals. In our study, we detected proviral DNA in Tregs. It was shown that Tregs might be more easily infected than CD4+CD25- T cells (not including memory T cells). But many details are far from being clear. We screened for the differences mRNA expressions in several tissues of SIV-infected monkeys. And we found that the transcription level of FoxP3 mRNA had been upregulated in the abdominal lymph nodes. Meanwhile, immuno-suppressive cytokines TGF-βand IL-10 increased at transcription level. TGF-β could suppress indirectly target cells through its crosstalk with dendritic cells. IL-10 could suppress target cells directly. So SIV-specific immunity might be dysfunctioned by Tregs.
语种中文
公开日期2010-11-12
源URL[http://159.226.149.42:8088/handle/152453/6478]  
专题昆明动物研究所_分子免疫药理学
推荐引用方式
GB/T 7714
李少遊. 调节性T细胞在SIVmac239感染中国恒河猴中的变化及其机制的初步研究[D]. 北京. 中国科学院研究生院. 2009.

入库方式: OAI收割

来源:昆明动物研究所

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