Immunohistochemistry with anti-CD31 antibody showing CD31 staining of vascular endothelium in human colon at 20x and 40x (B & C). Formalin fixed/paraffin embedded sections were subjected to heat induced epitope retrieval (HIER) at pH 6.2 and then incubated with rabbit anti-human CD31 antibody at 4.0 µg/ml for 60 minutes. The reaction was developed using MACH 1 universal HRP polymer detection system and visualized with 3’3-diamino-benzidine substrate (DAB).