中文摘要：

目的探讨CD4^-CD8^-双阴性T淋巴细胞（DNT细胞）的致病作用及其表面标志分子。方法取30只C3H／Hej小鼠，腹腔注射10pfu 3型鼠肝炎病毒（MHV3），采用磁珠分选和Cytotox96非放射性细胞杀伤活性测定方法，检测MHV3感染后0、4、15、30、40d脾脏DNT细胞分别对肝细胞、脾脏CD8^＋T淋巴细胞以及鼠巨细胞病毒感染后的脾脏CD8^＋T淋巴细胞的杀伤效应。免疫荧光抗体标记后，用流式细胞技术三色荧光分析法对脾脏内DNT细胞的表型进行检测。数据进行t检验或单因素方差分析，并用SN—K法进行差异显著性检验。结果MHV3感染后的DNT细胞对CD8^＋T淋巴细胞具有明显的杀伤作用，其杀伤作用随着效应细胞与靶细胞的比例增加而增强。感染15d时，当效靶比为1：1，2．5：1，5：1，10：1时，其杀伤效率分别为8．1％，38．6％，62．4％，90．3％。而对感染后的肝细胞以及非相关病毒感染的CD8^＋T淋巴细胞无明显杀伤效应。表型分析提示此群DNT细胞为一群全新的细胞群（TCRαβ^＋CD3^＋CD4^-CD8^-CD25^-CD28^-CD30^-CD44^＋）。结论 C3H小鼠感染MHV3后的TCRαβ^＋CD3^＋CD4^-CD8^-CD25^-CD28^-CD30^-CD44^＋细胞对同种病毒感染后的CD8^＋T淋巴细胞有特异性杀伤作用，提示该群细胞在慢性病毒性肝炎的发生和发展中起着一定的负性免疫调节作用，导致病毒感染慢性迁延。

英文摘要：

Objective To investigate role of CD4CD8 T cells in murine hepatitis virus type 3 （MHV-3） induced chronic viral hepatitis in C3H/Hej mice and to identify their surface markers. Methods Thirty C3H/Hej mice received 10 Pfu MHV-3 intraperitoneally, the CD4^-CD8^- T cells were isolated using magnetic bead sorting on 0, 4, 15, 30, 40 days post MHV-3 infection. The cytotoxic effects of CD4^-CD8^- T cells on normal and infected hepatocytes, CD8^＋ T cells and unrelated-virus （murine cytomegalovirus, MCMV） infected CD8^＋ T cells were examined by non-radioactive cytotoxicity assay. The surface markers of CD4^- CD^8- T cells were determined by flow cytometry. Results MHV-3 infected CD4^-CD8^- T cells showed significant cytotoxic effect on CD8^＋ T cells, but not on infected hepatocytes or MCMV infected CD8^＋ T cells. The analysis of cell surface markers demonstrated that the CD4^-CD8^-T cells are a completely new T cell subset. Conclusions CD4^-CD8^- T cells have significant cytotoxic effect on virus specific CD8^＋ T cells in MHV-3 infected C3H/Hej mice, which suggests that CD4^-CD8^- T cells have immune modulatory functions in the development of chronic viral hepatitis. The phenotype of these CD4^-CD8^- T cells detected by flow cytometry is TCRαβ^＋CD3^＋CD4^-CD8^-CD25^-CD28^-CD30^-CD44^＋.