KAHN TEST 175 
Typical, Antigen Titration for Test with Serum. 
Antigen suspension series. 
1. 
2. 
3. 
4. 
' 
Antigen + salt solution, cc. 
1 + 0.8 
1 + 0.9 
1 + 1 1 + 1.1 
1 + 1.2 
Heavy suspension of lipoid articles in each tube. 
Scheme used in testing solu- 
bility of lipoid particles in 
each antigen suspension 
Tube No. 
1. 
2. 
3. 
Antigen suspension, cc.' 
0.05 
0.025 
0.0125 
Salt solution, cc. 
0.15 
0.150 
0.1500 
Tubes are shaken three minutes; 1 cc. salt solution added 
to tube 1 and 0.5 cc. to other tubes. All are observed 
for particles. 
Solubility of lipoid particles as determined by 3-tube test. 
Particles 
not soluble. 
Particles 
not soluble. 
Particles 
soluble.2 
Particles 
soluble. 
Particles 
soluble. 
Standard antigen suspension 
o 
o 
+ 
+ 
+ 
If the antigen titration indicates that 1 + 1.2 produces a suspension 
of insohible lipoid particles, the titration has to be extended with 
increasing amounts of salt solution (1.3, 1.4, 1.5, etc.) until that amount 
of saline is found in which the lipoid particles completely dissolve. 
Determination of Antigen Sensitiveness.— When the antigen titer has 
been established, the next step is to determine the degree of sensitive- 
ness of the antigen employing standard antigen as a control. For this 
purpose, 10 sera may be used— selected preferably to give 1 strongly 
positive reaction, 1 negative reaction and 8 weakly positive reac- 
tions. If the sensitiveness of the new antigen is the same as that of 
the standard, the new antigen may be considered as standard; if more 
sensitive or less sensitive than standard, the new antigen is corrected 
as described below. 
Correction of Antigen.^— As already indicated, it is essential to 
establish a standard degree of antigen sensitiveness since heart muscle 
is resorted to in antigen preparation and, as is well known, different 
1 Each antigen suspension is allowed to stand thirty minutes after mixing antigen 
and salt solution before solubility test is made. 
2 Antigen + minimum amount of salt solution producing liijoid particles which 
dissolve in salt solution. 
3 For a recent discussion of this phase of antigen standardization see Kahn, R. L.: 
Kendrick, P. L. and Nagle, N.: Studies on Antigen for the Kahn Test, Jour. Infec. Dis., 
1927,41, HI. 
