The Croonian Lecture A contribution to human biochemical genetics ; the chemical basis of blood-group specificity

In 1900 Landsteiner published the first of his fundamental discoveries which resulted in the division of human bloods into distinct groups and laid the foundation of our present-day knowledge of the specificity of human blood. He showed in a series of simple experiments that when serum and erythrocytes obtained from different persons were mixed together agglutination of the erythrocytes frequently took place, but that in some mixtures no agglutination occurred. It was deduced from these results, and other observations which were obtained somewhat later, that, according to whether or not the red cells contained one or two factors (later designated quite arbitrarily as factors A and B) or neither factor, human bloods could be classified into four groups. The serologically specific agent in the serum, the anti-A or anti-B agglutinin, occurs naturally and brings about the agglutination of those red cells which contain the A or B factors respectively. Antibodies which agglutinate group O cells specifically are not normally found in man and it is, therefore, not possible to detect group O cells directly. Landsteiner concluded from these studies that a person’s serum cannot contain antibody for antigens present in his own erythrocytes, and a definite relationship between different kinds of human blood was revealed and subsequently developed into what is now known as the ABO blood-group system. The relationships, in modern terminology, are given in table 1.