Characterization and functional studies of the murine T-lymphocyte response to Mycobacterium leprae antigen

Mice were immunized with Mycobacterium leprae in incomplete Freund's adjuvant, and sensitized lymphocytes were obtained from draining lymph nodes. The lymphocytes thus obtained proliferated specifically in vitro in the presence of M. leprae antigen, and this response was shown to be both T-cell and macrophage dependent. T-cell blasts generated in vitro in response to M. leprae antigen were grown in the presence of interleukin-2 (IL-2). The proliferative response of these blasts to M. leprae antigen was strictly dependent on the presence of syngeneic spleen cells as antigen-presenting cells. M. leprae-immune F1 blasts responding to the antigen in the context of either parental H-2 haplotype-bearing accessory cell could be obtained by positive selection from an F1 hybrid-responding cell population. By means of flow microfluorometry the T-cell phenotype of the M. leprae-specific T-cell blasts was found to be Thy-1+ and to be composed of Lyt-1+ and Lyt-2+ subpopulations. Functionally, the blasts were shown to transfer delayed-type hypersensitivity locally to non-immunized recipients and to have cytolytic activity. Limiting dilution analysis showed the frequency of M. leprae-responding cells from blasts grown in IL-2 to be approximately 1/333.