| Abstract: | In reviewing the development in veterinary practice of comparative testing with tuberculins prepared from different types of mycobacteria for the purpose of separating cattle with specific and non-specific tuberculin sensitivity, it appeared that similar methods might be useful for the analogous problem of separating specific and non-specific tuberculin sensitivity in human populations. The results of a preliminary investigation along this line are reported in the present paper.Working in several parts of India, a special TRO research team tested more than 3,000 persons with serial doses of both a human and an avian PPD tuberculin corresponding to 1, 10, and 100 TU. An additional 6,000 were tested only with serial doses of human tuberculin.Presumptive evidence of non-specific sensitivity in some of the populations was found from the results of the tests with human tuberculin. Discrepancies in the frequencies of weak-dose and strong-dose reactors in different geographic areas, together with evidence from previous studies, suggested that most of the persons with strong-dose reactions could be regarded as having non-specific tuberculin sensitivity.RESULTS OF COMPARATIVE TESTS WITH HUMAN AND AVIAN TUBERCULINS FURTHER INDICATED THAT THE TUBERCULIN SENSITIVITY IN THE POPULATIONS STUDIED MUST BE CAUSED BY DIFFERENT SENSITIZING AGENTS: one producing a high degree of sensitivity brought out more effectively by the human than by the avian tuberculin, the other producing a low degree of sensitivity brought out more effectively by the avian than by the human tuberculin. The groups with high-grade sensitivity-those who react to the weak-dose test-can undoubtedly be regarded as having specific sensitivity, the kind caused by infection with virulent tubercle bacilli; the group who react only to the 100 TU test have apparently been sensitized by a different agent (or agents). Though the identity of the non-specific agent is still unknown, its antigenic properties would seem to be more closely related to avian than to human tuberculin. |
