Treatment with rhADAMTS13 reduces neutrophil infiltration and affects microthrombi events during myocardial ischemia/ reperfusion injury. After 1 hour of LAD occlusion and 23 hours of reperfusion, hearts from mice treated with either vehicle or rhADAMTS13 were harvested and sectioned for immunohistochemical analysis. (A) CD41 staining of heart sections. Adherent platelets, positive for CD41 (brown arrows), were seen only in some vessels and were detected only in vehicle, but not in rhADAMTS13-treated mice. Bottom: negative control staining without a primary antibody. (B) Gr-1–expressing neutrophils (brown color) infiltrated ischemic myocardium of vehicle-treated mice but significantly less did so in rhADAMTS13-treated mice. Bottom: Gr-1–positive cells in the ischemic area were counted in 5 different fields of view per section and numbers were expressed as positive cells per 1 mm2 of infracted area (3 mice per group, **P < .01). Scale bar = 100 μm.