Erythrocytes, also known as red blood cells (RBCs), develop in the fetal liver or the adult bone marrow. They are required for the delivery of oxygen to body tissues through the use of hemoglobin. Erythrocytes can also promote vasodilation by releasing ATP under conditions of shear stress and induce an immune response when they are lysed by pathogens. Normal human erythrocytes express CD36, an adhesion molecule of monocytes, platelets, and endothelial cells. Erythrocytes that lacked CD47 were rapidly cleared from the bloodstream by splenic red pulp macrophages. CD71 could exclude mature erythrocytes, thrombocytes and reticulocytes and improve these specific label and sorting purity.