434 The Philippine Journal of Science 192a 



become undemonstrable in a system designed for a maximum 

 of 0.1 cubic centimenter of serum. 



It is thus evident that the strain of B. tuberculosis used in 

 these tests fulfills two important requisites for an antigen suit- 

 able for use in measuring immunologically the effect of treat- 

 ment of leprosy with chaulmoogra oil and its products. In cases 

 during early treatment it has given 100 per cent positive reac- 

 tions and, for the most part, complete fixation. A very high 

 percentage of positive results in untreated cases is a sine qua 

 non if the method is to be of practical application. Secondly, 

 with this antigen a measurable weakness in complement-fixing 

 strength of sera in cases clinically and bacteriologically negative 

 under treatment has been demonstrated, and the reaction may 

 become negative within a reasonable time after disappearance of 

 acid-fast bacilli from superficial lesions. 



To be ideal, an antigen for this purpose should be absolutely 

 specific for leprosy, but in this respect B. tuberculosis fails. 

 For practical purposes, however, specificity of an antigen in a 

 test to measure the decrease in complement-fixing strength is 

 not so essential as in a similar test for diagnostic purposes, 

 for here one starts with a positive fixation in cases already 

 proven bacteriologically to have leprosy. In view of the close 

 serological relation of complement-fixing substances in serum 

 of animals immunized to various members of the acid-fast group, 

 it is very doubtful if a specific antigen for leprosy not reacting 

 with serum from human tuberculosis will ever be found. A 

 complicating tuberculous infection cannot be excluded in cases 

 of leprosy giving complement fixation with an antigen of B. 

 tuberculosis. This, however, is not an insuperable objection to 

 the test as proposed; for the majority of cases showing no 

 clinical evidence of active tuberculosis will presumably, according 

 to the above observations, show a diminution of complement- 

 binding strength with improvement of leprous lesions, in which 

 case active tuberculosis may be excluded. Those cases in which 

 a complicating active tuberculosis is a factor in producing com- 

 plement fixation, provided the tuberculous infection improves 

 with the disappearance of leprous lesions, may show a weakening 

 or a loss of complement fixation ; for it has been observed that the 

 strength of a positive reaction in tuberculosis appears to bear 

 some relation to the severity of the disease, and reactions 

 becoming gradually weaker until they became negative have 

 been frequently noted (6) with clinical improvement and "cure." 

 Under these circumstances the test will still be a valuable index 



