1 1 6 AGGLUTINATION 



Still more interesting is the observation that there are hem- 

 Isohemag- agglutinins against the red cells of different animals even of 

 glutinins. the same species, so-called Isohemagglutinins or Isoagglutinins. 

 These have thus far been demonstrated in the bloods of dogs 

 (Von Dungern) steers and rabbits (Ottenberg and Friedman). Isoagglut- 

 inins in the human serum were discovered independently by Landsteiner 

 and Shattock in 1900. At first the occurrence of isoagglutination was 

 regarded of pathological significance, but soon it was shown that the 

 phenomenon occurred with a large percentage of normal bloods. In fact 

 all human bloods can be divided into four sharply defined groups according 

 to the way in which they interagglutinate. The groupings can be explained 

 by assuming the existence of two agglutinins of which the first group 

 possessed both, the second one, the third one, and the fourth neither. 

 In each case the cells are susceptible only to that agglutinin which does not 

 exist in the individual's own serum. Thus: 



The serum of the first group, designated as group I, possesses the power 

 of agglutinating the red cells of members of all the other groups but the 

 red cells of members of group I are not agglutinated by any human serum. 

 This group includes about 50 per cent, of all persons examined. 



The serum of the members of the second group agglutinates the red cells 

 of members of the third and fourth groups. The cells of members of the 

 second group are agglutinated by sera of individuals of groups I and III. 

 The serum of group III agglutinates cells of persons belonging to members 

 of the second and fourth groups; its cells are agglutinated by sera of the 

 first and second groups. 



The fourth group, whose members are relatively rare, is characterized 

 by possessing no agglutinin for human red cells and by its cells being 

 agglutinable by the sera of all other groups. 



The group characteristics are permanent for each individual through- 

 out his life. When concentrated, the agglutinins act almost instantane- 

 ously; when diluted they act more slowly. Agglutination occurs in the 

 cold as well as at high temperatures. The peculiar groupings are not only 

 permanent with the individual but they are hereditary. Von Dun- 

 gern and Hirschfeld have conclusively proved that agglutinins are 

 hereditary and follow the Mendelian law. This observation had, 

 however, been made long before this in a paper by Epstein and Otten- 

 berg (1908). 



With the recently increasing popularity of blood transfusions, the 

 phenomena of isoagglutination and hemolysis, the two being very closely 

 related, have attained a more practical significance. In selecting donors 

 for a transfusion, agglutination and hemolysis tests should always, when 

 time permits, be made before operation. These tests in vitro are usually 

 a safe guide as to conditions in vivo. That donor should be chosen who 



