The results confirm the reports by previous observers that the sera of lepers react with tubercle antigen and, further, demonstrate by the quantitative complement-fixation test a high degree of reactivity. In this test for syphilis, our findings fail to confirm the results of other tests reported in the literature in which fairly high percentages of reactions occurred. In fact, for the most part, the reactivity of the leprosy sera was practically absent even when there was a high degree of activity with the tubercle antigen, and the comparatively few definite reactions were obtained under conditions that fail to exclude syphilis.
The linear relationships characteristic of the reactions between tuberculous serum and antigen and of those between syphilitic serum and cholesterolized tissue extract were demonstrated in the tests of the leprosy sera with these antigens, except in two instances in which slight, atypical reactions occurred with the cholesterolized tissue extract.
Thus, with purified and accurately standardized antigens and with quantitative methods of testing, it is possible to evaluate more accurately than hitherto the activity of leprosy sera with the antigens used in the test for tuberculosis and syphilis.