Evaluation of Mycobacterium leprae immunogenicity via adoptive transfer studies

The immune response of mice to live, heat-killed, or autoclaved Mycobacterium leprae was investigated. After sensitization with 10(7) organisms in each group, recipient mice were transfused with the sensitized splenocytes 28 days later. A selected number of these mice were infected with 5 X 10(3) M. leprae, and the remaining animals were sacrificed at scheduled intervals for evidence of cell-mediated immunity to the M. leprae cell extract. Data from these and the bacteriological assays showed that all three materials induce cell-mediated immunity and also extend protection against the M. leprae challenge but not against a Listeria monocytogenes challenge. Adoptive immunity against M. leprae was expressed equally effectively in both non-irradiated animals and those sublethally (500 R) irradiated. This study reveals that, after adoptive transfer of immunity, a bacillary restriction occurs with concomitant onset of delayed hypersensitivity and that the protection observed could be specifically directed against an M. leprae challenge.