AGGLUTININS AND AGGLUTINATION 149 



one and not dependent upon the presence of cells. Agglutino- 

 gens are said to pass through dialyzing membranes, while agglu- 

 tinins do not. 



Properties of Agglutinins. Like most of the other 

 substances produced in immunity, agglutinins are precipitated 

 out of the serum in the globulin fraction (see Pick's table, 

 p. 140). All attempts to separate them from proteids have 

 been unsuccessful. Stark l found that trypsin does not attack 

 the agglutinins readily, corresponding to the resistance of the 

 serum proteids to this enzyme ; alkaline papayotin solution 

 destroys them slowly, while pepsin acts much more rapidly. 

 Alkalies are destructive even when quite dilute, while acids 

 are much less harmful. The temperature resistance of agglu- 

 tinins seems to be variable, plague agglutinin being destroyed at 

 56, while purified typhoid agglutinin may resist 80-90 ; 

 most agglutinin serums lose their property at 60 65. The 

 rate of reaction of agglutinins increases with the temperature, 

 as long as this is not high enough to injure the reacting sub- 

 stances. 2 



The structure of the agglutinins (in the Ehrlich theory) is sim- 

 ilar to that of the toxin ; i. e., there is a haptophore group by 

 which they combine with the agglutinogen, and a toxophore 

 group by which they produce the changes that cause agglutina- 

 tion. The agglutinogen is probably related to the antitoxins in 

 structure, having a single haptophore to unite with the agglu- 

 tinin. By degeneration of the toxophorous group of the 

 agglutiniu, agglutinoids may be formed. It is believed that 

 agglutinins are cell receptors, which have a group with a chem- 

 ical affinity for the agglutinogen of the bacterial protoplasm, 

 and also another group which brings about the agglutination. 

 They are, therefore, more complex than the simple receptors 

 that unite with toxins, and are called receptors of the second 

 order. 



Just what constituent of the bacteria acts as the stimulus to 

 the production of the agglutinin is unknown. Apparently, 

 there are at least two bacterial substances with this property, 

 one of which seems not to be a proteid, since it is soluble in 

 alcohol and gives no biuret reaction, and resists temperature up 

 to 165. The other gives all proteid reactions, and is destroyed 

 by heating to 62. We consider, therefore, that there are two 

 agglutinogens in the bacterial cell, one, thermostable, the other, 

 thermolabile. The difference in the function of these two 



1 Inaug. Dissert., Wurzburg, 1905. 



2 Madsen, et al., Jour. Exper. Med., 1906 (8), 337. 



