Platelet binding to HUVEC. Nonactivated or thrombin-activated, washed, and calcein-loaded platelets were allowed to adhere to normal, apoptotic or thrombin-stimulated HUVEC for 20 minutes. Apoptosis was induced either by staurosporine or by suspending cells with serum deprivation. Platelet binding was then determined by flow cytometry to exclude involvement of subendothelial matrix proteins. Binding is expressed as the median fluorescence (FL-1-H) of the entire HUVEC population. Apoptotic HUVEC bound nonactivated platelets as effective as normal HUVEC bound thrombin-activated platelets. A representative experiment of three performed is shown.