Membrane FasL expression on HUVECs. HUVECs were incubated for 16 hours with or without 1–100 μM H2O2 or 0.5% and 0.5 and 1% CSE, in the presence or absence of 500 U/ml catalase. Membrane FasL expression on HUVECs analyzed by cell-monolayer-based spectrofluorimetry (A and B) and flow cytometry (C). (A and B) Data are reported as the means ± SEM of the values obtained from 5 experiments. *p < 0.05, **p < 0.01 vs. cells not exposed to H2O2 or CSE. †p < 0.05 vs cells exposed to 1% CSE only. (C) Data are representative of 3 separate experiments. Background; fluorescence levels generated by replacement of anti-FasL antibody with nonimmune IgG.