脐血造血干/祖细胞表面CD95/Fas抗原和Bcl-2的表达和功能研究

对人脐血干 /祖细胞表面CD95 /Fas抗原及Bcl 2的表达和功能特征进行了研究。新鲜分离的脐血CD34+细胞表达低水平CD95 ,体外培养中联合应用细胞因子如SCF和FL可上调CD95表达 ,负调控因子例如肿瘤坏死因子 α(TNF α)和干扰素 γ(IFN γ)可进一步增加其表达量。将CD34+ 细胞与抗 CD95单克隆抗体共同孵育 ,通过活细胞记数、流式细胞术、集落形成细胞 (CFU C)及长期培养启动细胞 (LTC IC)的分析 ,研究了CD95介导的功能特性。抗 CD95单抗与TNF α或IFN γ组合条件下 ,活细胞记数和CFU C计数分别为 31.9± 11.2和 4 3± 2 .0 ,LTC IC生成受到抑制 ,细胞凋亡率为 4 2 .9± 12 .4。而抗 CD95单抗在无细胞因子存在条件下或抗 CD95单抗与早期效应细胞因子SCF和FL组合条件下诱导的凋亡率很低。细胞浆内增加的Bcl 2水平和脐血CD34+ 细胞表面CD95的关系表明Bcl 2可能对CD95介导的CD34+ 细胞的凋亡起保护作用。

Expression and Function of CD95/Fas Antigen and Bcl-2 on Cord Blood Hematopoietic Progenitor Cells

The cell-surface expression and functional status of the CD95/Fas antigen on primitive hematopoietic progenitors isolated from human cord blood were studied. The CD34(+) cells freshly isolated from cord blood displayed low CD95 expression, combinations of cytokines such as SCF+FL upregulated the expression of CD95 in CD34(+) cells. Tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) further increased the CD95 expression induced by positive cytokines. The functional status of CD95-mediated apoptosis was analysed by incubation of CD34(+) cells in the presence of anti-CD95 monocloned antibody (McAb). The effect of anti-CD95 McAb was measured by viable cells counting, flow cytometry, LTC-IC and CFU-C assays. Viable cells and CFU-C numbers were 31.9 +/- 11.2 and 43 +/- 2.0 respectively, the rate of apoptosis was 42.9 +/- 12.4 in the presence of anti-CD95 McAb and TNF-alpha or IFN-gamma. However, growth factor deprivation or the early-acting cytokine such as SCF and FL cross-linking of CD95 lead to low apoptosis of CD34(+) cells. The correlation of increased intracytoplasmic levels of Bcl-2 and the presence of CD95 on surface of CD34(+) cells suggests that Bcl-2 may be involved in protecting against CD95-mediated apoptosis of cord blood CD34(+) cell.