Expression of ABCG2 protein on peripheral mature red blood cells. Peripheral blood from mice, rhesus macaques, and humans were collected, stained with primary antibodies recognizing respective ABCG2, and analyzed by flow cytometry. (A) Red blood cells from Abcg2^-/- mice (shaded area) or wild-type mice (solid line) stained with anti-Abcg2 antibody Bxp-53. (B) Rhesus macaque red blood cells stained with either isotype control antibody (shaded area) or anti-ABCG2 antibody Bxp-21 (solid line). (C) Human red blood cells stained with either isotype control antibody (shaded area) or anti-ABCG2 antibody 5D3 (solid line).