FACS analysis of apoptotic HUVEC, ie, cells with subdiploid DNA weakly stained with fluorescent propidium iodide18 (M1 region), in comparison with nonapoptotic HUVEC, ie, strongly stained cells with diploid DNA (M2 region). HUVEC were cultured in (A) complete medium supplemented with VBL 0.25 pmol/L or (B) 1 pmol/L; (C) the medium alone (negative control), or (D) supplemented with dexamethasone 1 mmol/L, an apoptogenic drug19 (positive control). Treatments on days 0 and 2, analysis on day 4. FL2-H = axis of relative fluorescence intensity. One representative experiment out of four.