284 Blood Groups 



agglutinogens causes the formation of both types of agglutinins 

 in group O individuals, of H2 agglutinin in individuals of group 

 Hi, of Hi agglutinins in rabbits of group H2, but does not cause 

 any agglutinins in rabbits of the fourth group, H1H2. 



The A-B Blood Groups in Human Beings 



Blood groups in human beings are also controlled by multiple 

 alleles. Actually, there are several sets of blood groups in man. 

 Those which are best known and chiefly determine whether or 

 not transfusions can be made are the Landsteiner or A-B blood 

 groups. Like rabbits, human beings can have two agglutinogens, 

 designated A and B; and any person may have either, both, or 

 neither. Persons with agglutinogen A only belong to group A; 

 those with agglutinogen B only, to group B; a person with both 

 agglutinogens is in group AB; a person with neither belongs in 

 group 0. If only the agglutinogens are considered, this situ- 

 ation is very much like the one just described for rabbits; but 

 when the agglutinins are considered, the two cases are very 

 different. Rabbits normally possess no agglutinins, but certain 

 agglutinins may be developed in their bodies by the injection of 

 certain agglutinogens. In human beings, however, the agglu- 

 tinins corresponding to the A and B agglutinogens are already 

 present in the serum (or plasma) of certain individuals and are 

 not merely the result of a reaction caused by an injection. Some 

 individuals have the agglutinin or antibody for A, some have 

 the agglutinin for B, some have both agglutinins, and others 

 have neither. Obviously, nobody has the agglutinin (antibody) 

 for any agglutinogen (antigen) which he may carry, for if he 

 did, his own blood would have been agglutinated in early devel- 

 opment and he would not have survived. When a human adult 

 lacks a certain antigen, he always has the corresponding anti- 

 body (Landsteiner's rule). Nobody, therefore, lacks both anti- 

 gens and both antibodies. The agglutinin specific for agglutino- 

 gen A is usually designated as alpha or anti-A, that specific for 

 agglutinogen B is beta or anti-B. 



The method of inheritance of the blood groups indicates that 

 a series of three multiple alleles is operative (Bernstein's theory). 

 A recessive gene is assumed to produce no isoagglutinogen and 

 individuals homozygous for this gene belong to group 0. A 

 dominant allele in the series results in the production of agglu- 



