38 



Scientific Proceedings (70). 



If the precipitating antibody is heated at 72 0 for one half hour, 

 it loses its precipitating functions, but retains its sensitizing power, 

 though somewhat diminished. Such heated precipitin, some- 

 times described as " precipitinoid," is known to retain its com- 

 bining power with antigen. One may conclude, therefore, that 

 the combining power, but not the precipitating power, of antibody 

 is essential in anaphylaxis. 



Precipitating antibody heated at 72 0 for one half hour has 

 lost its capacity to bind complement in the presence of antigen. 

 However, it still retains its sensitizing value. These facts are 

 illustrated by the following experiment. 



The serum of a rabbit, immunized to crystallized egg albumen, 

 is diluted with three volumes of salt solution. Part of this 

 diluted serum is heated at 56 0 for one half hour to destroy com- 

 plement, and part of it is heated at 72 0 for one half hour to destroy 

 the precipitating function. In the following table the amounts 

 of diluted serum employed are reduced to correspond to the 

 amount of serum therein contained. The method employed is 

 that of complement fixation. 



Complement Fixation Test. 





1 



2 



3 



4 



5 



6 



Precipitation. 



S. 56° 



S. 72 0 



Salt solution 



G. P. comp 



o.S 

 0.001 



O.I 



o.S 



O.I 



O-S 



O.OOI 

 O.I 



o.S 

 0.1 



0.001 

 0.1 



o.S 

 0.0s 



0-5 

 O.OOI 



o.S 



O.OOI 



Precipitation 















++ 





After incubation for one hour, one c.c. of well-sensitized cells 

 was added to each of the tubes. Hemolysis was complete in 

 tubes 2 to 6 after one half hour, but had not even begun in 1. 

 On the following day tube I showed slight hemolysis. The test 

 was made with the usual additional controls. The result shows 

 that the serum heated at 72 0 does not bind complement. The 

 precipitation reaction shows that it does not precipitate. A series 

 of normal guinea-pigs were injected with graded amounts of the 

 same heated serums used in the above experiment, and were 

 injected two days later with egg albumen to test for passive 

 sensitization. Serum heated at 72 0 sensitized in amounts of 0.3 



