Affinity-purified human anti-Neu5Gc antibodies bind specifically to Neu5Gc on endothelial cells of aorta sections and vasa vasorum. Affinity-purified human anti-Neu5Gc antibodies were used as a primary reagent on cryosections of autopsy samples of aorta. (A) Sections were incubated with the biotinylated, affinity-purified human anti-Neu5Gc antibodies followed by rabbit anti-biotin and then Cy3-anti-rabbit, with nuclear counterstaining using DAPI (top). Antibody staining was abrogated by adsorption with chimpanzee serum (middle) or by previous sialidase pretreatment (bottom). A representative example of 5 independent experiments is shown. (B) Sections were incubated with biotinylated, affinity-purified human anti-Neu5Gc antibodies followed by mouse anti-biotin and FITC antimouse antibody and nuclear counterstaining with DAPI. Primary antibody staining was abrogated by addition of Neu5Gc2Me but not by Neu5Ac2Me. The staining pattern is appreciated in both aorta and vasa vasorum. A representative example of 3 independent experiments on 8 individuals is shown (magnification ×200).