Increased expression in erythrocytic Ii antigens in sickle cell disease and sickle cell trait

The reactivity of human erythrocytes with anti-I and anti-i sera was estimated in 36 normal adults, 18 individuals with sickle cell anemia and 27 individuals with sickle cell trait, by quantitative hemagglutination with a sensitive autoanalyzer system. SS erythrocytes showed significantly increased I and i reactivity when compared to normal erythrocytes. AS erythrocytes also demonstrated some increase in Ii reactivity. No correlation was found between erythrocytic HbF content and i reactivity.