286 AGGLUTININS 



In a mixed infection due to two or more varieties of bacteria there 

 iwill be specific agglutinins for each of the microorganisms, and group 

 agglutinins for each of them as well. If the immune serum is saturated 

 with one of these varieties its chief or major agglutinins and some or all 

 of the group agglutinins will be removed, but the major agglutinin of the 

 second species will remain. On the addition of the second bacterium to 

 the immune serum agglutination occurs and its agglutinin is absorbed. 

 Park, who has carefully investigated this subject, finds that the absorp- 

 tion method proves that when one variety of bacteria removes all agglu- 

 tinins for a second, the agglutinins in question were not produced by the 

 second variety. 



Hemagglutinins. Agglutination, like other immunity reactions, is a 

 manifestation of broad biologic laws and is not limited to bacteria. As 

 hemolysins are produced by the injection of an animal with red blood- 

 corpuscles from another species, so agglutinins that agglutinate the red 

 blood-corpuscles may be developed at the same time. When a serum 

 containing hemagglutinin is added to a suspension of the corresponding 

 red blood-corpuscles contained in a test-tube, it causes these to collect 

 into clumps and flakes and sink to the bottom, just as a typhoid immune 

 serum agglutinates typhoid bacilli. These clumps are broken up with 

 some difficulty, and may interfere with hemolytic reactions. They are 

 especially to be observed in antihuman hemolytic serums when agglu- 

 tination may be so marked as to prevent hemolysis unless the tubes are 

 frequently and vigorously shaken. 



Small amounts of normal hemagglutinins may be found. Of par- 

 ticular practical importance are those for animals of the same species, 

 the so-called isohemagglutinins. 



Isohemagglutinins and their Relation to Blood Transfusion. Isohem- 

 agglutinins were discovered independently by Landsteiner, 1 and Shattuck 

 in 1900, and have been studied quite extensively by Hektoen, Otten- 

 burg, 2 Moss, 3 Gay, Brem, 4 and others. At first the occurrence of isoag- 

 glutination was regarded as of pathologic signifiance, but later researches 

 showed that they may be found in a large percentage of normal bloods. 

 According to Landsteiner, human bloods may be divided into three 

 groups; the fourth group was discovered independently by several ob- 

 servers. 



Group 1: Here the corpuscles are not agglutinated by any human 



1 Wien. klin. Wochenschr., 1901, xiv, 1132; 



2 Jour. Exper. Med., 1911, 13, 425; ibid., 536. 



3 Bull. Johns Hopkins Hosp., 1910, 21, 63. 



4 Jour. Amer. Med. Assoc., 1916, 67, 190. 



