Comparison of various preparations of Mycobacterium leprae and other mycobacteria by lymphocyte stimulation.

Peripheral blood lymphocytes were stimulated in vitro with different mycobacterial antigen preparations and responses were measured as incorporation of tritiated thymidine. Blood donors were 9 patients with lepromatous leprosy, 16 tuberculoid leprosy patients, and 6 healthy individuals with different degrees of exposure to leprosy. The results revealed a good correlation between the responses to M. leprae from human sources and bacilli from armadillos inoculated with human leprosy bacilli, although the latter were less potent stimulators. Responses to BCG and PPD did not correlate with lymphocyte responses to human M. leprae. Acid-fast bacilli grown on LA-3 medium inoculated with human leprosy bacilli stimulated responses which did not correlate with responses to human M. leprae when positive responses were compared, but showed a good correlation when inhibitory effects of the bacilli on thymidine incorporation were studied. The significance of the lymphocyte stimulation test for identification of microbes is discussed.