Detection of endothelial apoptosis by annexin V staining. (A) HMVECs were incubated overnight in the presence (bottom) or absence (top and middle) of staurosporine. Cells were left untreated (top) or stained with FITC-labeled annexin V Ab (green) followed by fixation and visualization by confocal microscopy. DAPI (blue) was used to identify nuclei. (B) Annexin V staining in growth factor–deprived HMVECs incubated overnight with sera pooled from healthy donors (“control”) or obtained from individual patients with SCLS during acute episodes (10% vol/vol concentrations). Images in panel A were taken at 40× and enlarged and or at 160× in panel B.