ON ANTI-IMMUNE-BODIES 107 



serum 55. After an hour at 37 C. the corpuscles are 

 washed and the same amount of complement is added to 

 each. It is found that the resulting lysis is less in the case 

 of the corpuscles treated with anti-immune-body. The 

 difference is marked in the case of the ox's corpuscles ; 

 slight, though distinct, in the case of the rabbit's corpuscles. 

 Anti-immune-body thus apparently acts in the same way 

 on natural immune-bodies as on those produced by artificial 

 immunization. This is additional evidence, if such were 

 needed, that the immune-body naturally present in a serum 

 has the same constitution as that developed by active 

 immunization. 



(Note. The * complement ' used in these experiments was guinea-pig's 

 serum, which can be practically freed of the natural immune-body for ox's 

 corpuscles by contact with the corpuscles at 0C. In the case of the 

 immune-body for rabbit's corpuscles, however, so complete a result 

 is not obtained, though a certain amount of immune -body is taken up. 

 Thus the serum cannot be completely freed of its natural heemolytic 

 action. As there is, however, much more complement relatively than 

 natural immune-body, the action of anti-immune-body can quite well be 

 demonstrated. ) 



RELATION OF ANTI-IMMUNE-BODY TO THE COMBINATION 

 OF IMMUNE-BODY WITH RECEPTORS 



We have seen that the anti-immune-body acts by prevent- 

 ing the combination of complement with R + IB molecules. 

 We have, however, considered it advisable to investigate by 

 quantitative methods whether it has any action in prevent- 

 ing the union of immune-body with the receptors of the red 

 corpuscles directly. The principle is to test whether the 

 same amount of immune-body is taken up by the red cor- 

 puscles in the presence of anti-immune-body as when it is 

 absent. This is best done by observing the saturation point 

 of the red corpuscles with immune-body in the two condi- 

 tions ; that is, to find how many doses of immune-body must 

 be added before one dose remains free. 



