ISOHEM AGGLUTININS 183 



Extra Agglutinin 1. — hi July, 1929, Laiidsteiner and Levine 

 called attention to an extra agglutinin which they found in two 

 sera of group 0, three of group A, and one of group B. This 

 new agglutinin "gave reactions with bloods of various grou])s. " 

 In February, 1930, they report tlie results of further studies upon 

 this new agglutinin and designate it as "extra agglutinin 1." 

 They state that there is some apparent relationship between the 

 agglutinin and the P factor. 



In July, 1930, Nigg reported her studies of two unusual type 

 B bloods. Both contained an agglutinin demonstrable at 25° C. 

 for many type as well as type B cells. Agglutination did not 

 occur, however, at temperatures above 30° C. She concluded 

 that these agglutinins were identical with the "extra agglutinin 

 1" of Landsteiner and Levine. Since then, Landsteiner and 

 Levine (1931) have carried out extensive studies on "The Dif- 

 ferentiation of a Type of Human Blood by Means of Normal 

 Animal Serum." They conclude that this "extra agglutinin 1" 

 is specific for the P factor. Thus it is evident that occasionally^ 

 the serum of groups 0, A, or B individuals may contain an extra 

 agglutinin for an agglutinogen P that has been previously dis- 

 cussed. When a serum of this kind is encountered and compati- 

 bility tests are done at room temperature, some confusion may 

 result unless the phenomenon is understood. 



Irregular Isoagglutination at Temperatures Below 37° C. — If 

 one carries out agglutination tests using the sera and cells of 

 different individuals and varies the temperature between 37° and 

 0° C, he will observe many individual variations not distinguish- 

 able at body temperature. The number of these interesting vari- 

 ations increases as the temperature is lowered. Many of the re- 

 actions are due to the presence of a^ and a^ agglutinins and their 

 corresponding agglutinogens but others are not tlioroughly un- 

 derstood. 



AuTOAGGLUTiNiNS. — Landstcincr and Levine (1926) and Land- 

 steiner (1928) call attention to the frequent occurrence of auto- 

 agglutination at temperatures between 0° C. and 5° C. The 

 autoagglutinins can l)e absorbed by the homologous red cells at 

 0° C. and after washing with saline at the same temi3erature, tlie 

 agglutinins can be recovered by warming the suspension to 37° 

 C. or even less. Marked autoagglutination has been observed in 



