Biological activities of a murine T-cell clone with reactivity to Mycobacterium leprae.

Mice were immunized subcutaneously with killed Mycobacterium leprae in incomplete Freund's adjuvant and draining lymph nodes removed. Lymph node cells were propagated in vitro and cloned at limiting dilution in the presence of syngeneic accessory cells, antigen, and T-cell growth factor. Cloned T cells were restricted by the H-2I-A sublocus. In vitro interaction(s) of cloned T cells with accessory cells presenting M. leprae-derived determinants resulted in T-cell proliferation, interleukin secretion, and macrophage activation. The T cells were stimulated by killed M. leprae and M. bovis (strain BCG), but not Listeria monocytogenes, organisms indicating cross-reactivity between M. leprae and BCG at the clonal level. In vivo, cloned T cells induced protection against the "bystander" bacterium L. monocytogenes. These data suggest that the cloned M. leprae-reactive T cells are involved in acquired antimicrobial resistance.