Fas Antigen (CD95) in pure erythroid cell line AS-E2 is induced by interferon-γ and tumor necrosis factor-α and potentiates apoptotic death

We investigated the expression of Fas antigen (CD95) in the pure erythroid cell line AS-E2 in the presence and absence of interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α). TNF-α induced apoptosis in AS-E2 cells, whereas IFN-γ did not. In culture containing no IFN-γ or TNF-α, AS-E2 cells expressed little Fas antigen. However, IFN-γ and TNF-α both induced expression of Fas antigen and its mRNA within 24 hours after the stimulation. When anti-Fas monoclonal antibody (IgM) was added to AS-E2 cells after the induction of Fas expression, AS-E2 cells underwent apoptosis as shown by the induction of DNA fragmentation. This apoptotic change was inhibited by an inhibitor of caspase-3-like proteases (Ac-DEVD-CHO) and an inhibitor of CED-3/ICE family proteases (Z-Asp-CH2-DCB) but not by an inhibitor of caspase-1-like proteases (Ac-YVAD-CHO), suggesting a role for caspase-3-like proteases in Fas-receptor signaling. Although AS-E2 cells expressed Fas ligand mRNA, treatment with ZB4, an antibody that inhibits Fas-mediated cell death, failed to suppress IFN-γ– or TNF-α–mediated cytotoxicity. These findings suggest that the late erythroid progenitor cells are negatively regulated by IFN-γ and TNF-α, both of which are capable of inducing functional Fas expression.