Cell-mediated immunity in mice treated with Mycobacterium leprae or with macrophages harbouring M. leprae.

Following treatment of BALB/c or C3H/HeN mice in the hind footpads with irradiated Mycobacterium leprae, a marked enhancement of natural killer (NK) activity was observed in cells from the draining popliteal lymph node or from the spleen. NK activity was further enhanced when the treatment consisted of killed M. leprae which had been incorporated into mouse peritoneal macrophages. This effect was noted as early as 2 weeks after treatment and persisted for at least 9 weeks. Lymphoblastic transformation in response to suboptimal doses of the T-cell mitogen transformation in response to suboptimal doses of the T-cell mitogen concanavalin A or to M. leprae antigen was assayed in parallel in cells from the draining popliteal lymph node and from the spleen. In contrast to NK assays, treatment with M. leprae alone moderately altered the response to mitogen. However, there was a prominent enhancement of the T-cell response when treatment consisted of M. leprae-laden macrophages.