158 ANTIGENS AND THE TECHNIC OF SERUM REACTIONS 



when non-syphilitic serum is used. In addition, the following deter- 

 minations are sometimes desirable. 



The hemolytic titer, that amount of antigen which will of itself 

 cause lysis of red blood cells, and the antigenic titer, the amount of 

 complement it will absorb or "fix" in the presence of a definite amount 

 of specific syphilitic serum. 



The anticomplementary titration is made by mixing graded amounts 

 of antigen and a constant amount of complement (0.1 c.c. of a 10 per 

 cent, solution 1 ) with constant amounts (0.1 c.c.) of known syphilitic 

 serum and normal serum, both inactivated. 



The various mixtures are incubated in a water-bath at 37 C. for 

 an hour, then 0.2 c.c. of red blood cell suspension and inactivated 

 hemolytic serum are added and again incubated in the water-bath at 

 37 C. The maximum amount of antigen which will give complete 

 inhibition of hemolysis with syphilitic serum and no inhibition of 

 hemolysis in the non-syphilitic serum is regarded as the unit. 



EXAMPLE OF AN ANTICOMPLEMENTARY TITRATION OF ANTIGEN. 



Tube 5, containing 1.0 c.c. antigen, shows beginning inhibition of 

 hemolysis. This is regarded as the anticomplementary titer of the 

 antigen. 



As a general rule, the hemolytic titer is higher than the anti- 

 complementary titer. The test is readily made, if desired, by using 

 the same amounts of antigen mixed with 1 c.c. of red blood cell 

 suspension and sufficient salt solution to bring the volume to 4 c.c. 



It is customary to use one-fourth the anticomplementary titer as 

 the standard amount of antigen to be used in the actual test. In the 



1 Prepared by adding fresh normal guinea-pig serum to physiological salt solution 

 in the proportion of one part serum to nine parts salt. 



2 Serum control. 3 Hemolytic control. 



