Immunohistochemical analysis of apoA-I, MPO, and proteins modified by HOCl in human atherosclerotic intima. Photomicrographs of adjacent sections of an atherosclerotic coronary artery demonstrating immunostaining for apoA-I (A), proteins modified by HOCl (B), macrophages (C), and MPO (D) are shown. Positive immunohistochemical staining is indicated by a red reaction product. HOCl-modified epitopes colocalize with extracellular apoA-I (A and B, arrows), whereas MPO staining is primarily associated with macrophages (C and D, arrowheads). Original magnification, ×100; hematoxylin counterstain.