Fig. 3. Human ESCs express Fas on the cell surface at a lower level than do Jurkat cells. Fas expression does not change during decidualization in vitro. (A) Human ESCs and Jurkat cells were stained with a monoclonal anti-Fas antibody (filled histograms) and compared to cells stained with an IgG1 isotype control (white histograms) using flow cytometry. (B) The expression level of Fas as measured by MCFI. The signal derived from undifferentiated ESCs was set to 100 (**P<0.01: Jurkat versus undifferentiated and decidualized ESCs). (C) Fas mRNA expression was measured by semiquantitative real-time RT-PCR to compare undifferentiated and decidualized ESCs (n.s., non significant). Bars show the mean ± s.e.m. (D) Fas protein level was determined by flow cytometry to compare undifferentiated and decidualized ESCs. Filled histograms, ESCs stained with a monoclonal anti-Fas antibody; white histograms, ESCs stained with an IgG1 isotype control.