IMMUNOCHEMICAL STUDIES ON BLOOD GROUPS

Abstract

The immunochemical properties of purified A₁ and A₂ glycoproteins have been compared to ascertain whether their antigenic determinants differ. Quantitative precipitin and complement-fixation studies using several anti-A sera as well as purified γG anti-A antibodies clearly showed a specificity difference. This was also supported by absorption studies: A₂ substance specifically removed antibodies reacting with A₂ substance leaving anti-A₁ activity. A₁ substance was more effective than A₂ substance in dissolving an A₁ anti-A₁-specific precipitate. Purified γM anti-A hemolyzed A₁ cells more readily than A₂ cells. Inhibition studies using mono- and difucosyl type 2 A-active oligosaccharides showed that type 2 difucosyl receptors are present in A₂ substance. The structural basis for the specificity difference between A₁ and A₂ would appear to be that A₂ substances lack type 1 A determinants; this would account for the observed higher H and Le^b activity in A₂ substances.