280 INFECTION AND IMMUNITY 



goat immunized against the red blood cells of a sheep, they inac- 

 tivated it (destroyed the complement or alexin) by heating to 56 

 C. The serum then contained only the ''substance sensibilisatrice " 

 or immune body. To this inactivated serum they added sheep's 

 red corpuscles, without obtaining hemolysis. Having left the in- 

 active serum and the sheep's corpuscles in contact with each other 

 for some time, they separated them by centrifugalization. To the 

 supernatant fluid, they now added sheep-blood corpuscles and 

 normal goat serum (complement) and found that no hemolysis took 

 place. The immune body had apparently gone out of the serum. 

 The red cells which had been in contact with the serum and separated 

 by the centrifuge were then washed in salt solution and to them 

 complement was added in the form of fresh normal serum. Hemolysis 



Substance Complement 



Body Cell 



FIG. 32. EHRLICH'S CONCEPTION OF CELL-RECEPTORS, GIVING RISE TO IMMUNE 



BODIES. 



occurred. It was plain, therefore, that the immune body of the 

 inactivated serum had gone out of solution and had become attached 

 to the red blood cells, or, as Ehrlich expressed it, the immune body 

 by means of its ' * haptophore " atom-group had become united to the 

 corpuscles. In contrast to this, if normal goat serum (containing 

 complement only) was added to sheep corpuscles and separated again 

 by centrifugalization, the supernatant fluid was found to be still 

 capable of reactivating inactivated serum (immune body). This he 

 interpreted as proving that the complement was not bound to the 

 corpuscles directly. 



If the three factors concerned corpuscles, immune body, and 

 complement were mixed and the mixture kept at C., no hemolysis 

 occurred; yet, centrifugalized at this temperature, immune body 

 was found to have become bound to the corpuscles, the complement 

 remaining free in the supernatant fluid. If the same mixture, how- 

 ever, was exposed to 37 C., hemolysis promptly occurred. 



