Leukocyte subsets in the granulomatous response produced after inoculation with Mycobacterium leprae-BCG in lepromatous patients.

Leukocyte subsets present in the granulomatous response produced after the inoculation of a mixture of Mycobacterium leprae and BCG in lepromatous leprosy patients were characterized in situ using monoclonal antibodies and an immunoperoxidase technique. The granuloma produced after M. leprae-BCG inoculation showed a distribution pattern similar to tuberculoid granulomas. T lymphocytes bearing the CD8 phenotype (T cytotoxic/suppressor) were sequestered to the periphery of the epithelioid tubercles and T helper-inducer CD4+ lymphocytes were distributed throughout the infiltrate. Langerhans cells CD1+ were increased in the epidermis, and in dermis they were localized mainly in the mantle surrounding the granuloma. Most of the dermal infiltrate produced after the inoculation or M. leprae-BCG expresses the HLA-DR antigen. Similarly, most keratinocytes were also positive to this MHC antigen. The granulomatous response to BCG was similar to the inoculation of a mixture of M. leprae-BCG, however acid-fast bacilla were still present. The inoculation of M. leprae produced a macrophage granuloma with no clearing of the bacilla which resembles the lepromatous leprosy granuloma.