Functional expression of CD95/fas antigen and Bcl-2 on cord blood hematopoietic progenitor cells

Abstract

The cell-surface expression and functional status of the CD95/Fas antigen on primitive hematopoietic progenitors isolated from human cord blood (CB) were studied. The CD34⁺ cells freshly isolated from CB displayed low CD95 expression. The combinations of cytokines such as SCF+FL could up-regulate the expression of CD95 in vitro culture and tumor necrosis factor-α (TNF-α) and interon-γ (IFN-γ) further increased the CD95 expression induced by positive cytokines. The functional status of CD95-mediated apoptosis were analyzed by incubation of CD34⁺CB cells in the presence of anti-CD95 monoclonal antibodies (McAbs). The effects of anti-CD95 McAbs were measured by viable cell counting, flow cytometry, LTIC and CFU-C assays. A decrease of viable cells, CFU-C and LTIC numbers were observed in the presence of anti-CD95 McAbs and TNF-α or IFN-γ. However, growth factor deprivation or the early-acting cytokine such as SCF and FL cross-linking to CD95 caused low apoptosis of CD34⁺ cells. The correlation of increased intracytoplasmic levels of bcl-2 and the presence of CD95 on fresh CB CD34⁺ cells suggested that bcl-2 might be involved in protecting against CD95-mediated apoptosis of CB CD34⁺ cells.

Keywords

CD95/Fas / Bcl-2 / expression / cord blood / CD34⁺ cells

References

[1] YangX, Khosravi-FarR, ChangH Y. A novel Fasbinding protein that activates JNK and apoptosis. Cell Immunol, 1997, 140: 197-197

[2] SudaT, HashimotoH, TanakaM, et al. . Membrane Fas ligand kills human peripheral blood T lymphocytes and soluble Fas ligand blocks the killing. J Exp Med, 1997, 186: 2045-2045

[3] ZhangJ, CadoD, ChenA, et al. . Fas-mediated apoptosis and activation-induced T-cell proliferation are defective in mice lacking FADD/Mort-1. Nature, 1998, 392: 296-296

[4] PapoffG, StassiG, De MariaR, et al. . Constitutive expression in thyrocytes. Science, 1998, 279: 20'5a-20'5a

[5] BarcenaA, ParkS W, BanapourB, et al. . Expression of Fas/CD95 and Bcl-2 in the primitive hematopoietic progenitors in human fetal liver. Blood, 1996, 88: 2013-2013

[6] BarcenaA, MuenchM O, SongK S, et al. . Role of CD95/Fas and its ligand in the regulation of the growth of human CD34⁺CD38-fetal liver cells. Exp Hematol, 1999, 27: 1428-1428