HS4C3-Binding Epitope Contributes to Fas Signaling Figure 3. The expression of Fas increased on the surface of cells overexpressing 3OST-5. (A) FACS analysis of cell surface Fas (left panel) or total Fas (right panel) in cells overexpressing 3OST-5 using an anti-Fas antibody (black line, control cells; red line, cells overexpressing 3OST-5). The gray line shows the result obtained from cells not treated with primary antibody. As described in Materials and Methods, mESCs were permeabilized to observe total Fas expression or not permeabilized to observe Fas expression on the cell surface. (B) FACS analysis, using an anti-Fas antibody, of Fas on the surface of cells that were overexpressing 3OST-5 and had been treated with brefeldin A. The histograms show the ratio of the mean fluorescence intensity of the treated cells to that of non-treated control cells (arbitrary value = 1). Values are the means 6 SD. (C) FACS analysis of cell surface Fas in mESCs cultured for 8 days in the absence of LIF using an anti-Fas antibody. In the left panel, a histogram shows a representative result of the FACS analysis (black line, in the presence of LIF; red line, in the absence of LIF). The gray line shows the result obtained from cells not treated PLOS ONE | www.plosone.org 7 August 2012 | Volume 7 | Issue 8 | e43440