Photomicrographs of microthrombus, SED, TUNEL staining, and immunohistochemical staining for CD34- and CD68-expressing cells on TUNEL-positive slides. Microthrombus (A) and SED with associated reactive endothelial cells (B) are seen in the splenic section of a representative TTP patient. H&E stain and PAS stain, respectively. TUNEL is positive in the splenic red pulp of a TTP patient (C) and negative in a control patient (D). Methyl green counterstain. Double staining for CD34- or CD68-expressing cells on TUNEL-positive TTP slides demonstrates the presence of apoptotic ECs (E) and apoptotic bodies in the cytoplasm of macrophages (F). Hematoxylin counterstain. Original magnification × 400 for all sections.