ABO blood group system letter O for "ohne", meaning without or zero; Landsteiner chose the latter.) This classification was adopted by the National Research Council and became variously known as the National Research Council classification, the International classification, and most popularly the "new" Landsteiner classification. The new system was gradually accepted and by the early 1950s, it was universally followed. The first practical use of blood typing in transfusion was by an American physician Reuben Ottenberg in 1907. And the large-scale application started during the First World War (1914-1915) when citric acid was developed as blood clot prevention. Felix Bernstein demonstrated the correct blood
ABO blood group system The resulting red blood cells do not usually express A or B antigen at the same level that would be expected on common group A or B red blood cells, which can help solve the problem of an apparently genetically impossible blood group. The table above summarizes the various blood groups that children may inherit from their parents. Genotypes are shown in the second column and in small print for the offspring: AO and AA both test as type A; BO and BB test as type B. The four possibilities represent the combinations obtained when one allele is taken from