Influence of Mycobacterium leprae and its soluble products on the cutaneous responsiveness of leprosy patients to antigen and recombinant interleukin 2.

Experiments were carried out in the skin of patients with leprosy to examine whether suppressor cell populations either exist in the skin of multibacillary lepromatous leprosy patients, can be activated with antigen, or are induced to emigrate into a cutaneous site from the circulation. For this purpose, purified protein derivative of tuberculin, a delayed-type antigen that generates a cell-mediated immune response, was introduced into the skin alone or with nonviable Mycobacterium leprae bacilli. Areas of induration and the resulting numbers and phenotypes of emigratory cells were not influenced by M. leprae and its products. Further studies examined the ability of M. leprae and its soluble products to modify the cutaneous response to intradermal injection of recombinant interleukin 2 (IL-2), a lymphokine that mimics a cell-mediated response. Neither the simultaneous injection of M. leprae and IL-2, nor the prior injection of M. leprae followed in 2 days by IL-2, nor the prior administration of IL-2 followed in 4 days by M. leprae, into the same skin site, modified the zone of induration generated by IL-2. In addition, the immunocytochemical and histopathological evaluation of biopsy specimens of skin sites showed no difference between sites injected with IL-2 and sites injected with IL-2 and M. leprae. We conclude that suppressor T cells, if they exist, do not influence the gross or microscopic responsiveness of a cell-mediated skin reaction to antigen and IL-2. IL-2 did, however, enhance the responsiveness of skin-test-positive tuberculoid patients and family contacts to M. leprae antigens by a synergistic effect on the zone of induration and local cell accumulation.