Introduction

Significance

Of all the blood group systems the ABO system is by far the most important. It is the only system where if you lack an antigen, you always have the corresponding antibody. Moreover, anti-A and anti-B are potent hemolysins capable of causing intravascular hemolysis by bind complement to C9. This is why, in blood transfusion, the ABO of the patient and donor must be compatible.

This module discusses the ABO system at a basic level. It does not cover some topics in depth and does not include more complex topics such as a detailed survey of all the group A subgroups and para-Bombays.

Discovery: The ABO BGS, the first system discovered, was discovered by Karl Landsteiner in Vienna in 1900. Landsteiner mixed the sera and cells of his colleagues together and noticed that some sera could agglutinate some cells. He postulated that 4 groups were possible (A, B, O, and AB), although the AB group was not found until 1902 by two of his students.

See history of blood transfusion for this and other key discoveries.

Like many discoveries, the full relevance of Landsteiner's work was not realized until years later. His discovery of ABO was finally recognized by the awarding of the Nobel Prize in physiology or medicine in 1930.

Frequencies: Frequencies of the 4 groups show racial and geographical variations (Table 4-1). For example, the B and AB groups have a higher frequency among Orientals than among North American Caucasians.

Table 4-1. Racial variations in ABO blood groups.

Other racial differences exist. For example, all pure blooded Canadian Indians are group O.

Introduction