Effects of endothelial injury, platelet interactions and shear stress on PMN rolling. Rolling of activated PMN (mean ± SEM; n = 4) on an endothelial lesion covered with platelets (filled symbols) or intact endothelium (blank symbols) under maximal and sub-maximal activation. (a) activation with 100 ng/ml LPS (HUVEC++/PMN++/PLT vs. HUVEC++/PMN++), and (c) activation with 10 ng/ml LPS (HUVEC+/PMN+/PLT vs. HUVEC+/PMN+). (b and d) show the corresponding curves for predicted rolling-fractions determined by ANCOVA of logarithms (continuous line: intact HUVEC, discontinuous line: injured HUVEC with platelets). In contrast to intact HUVEC, rolling fractions on platelet-covered endothelial lesions remained low at both LPS concentrations and all levels of shear stress (P < 0.01, ANCOVA).