Immunohistological analysis of nerve granulomas in neuritic leprosy

Immunohistological analysis of infiltrates of nerves in patients with neuritic leprosy was carried out using monoclonal antibodies defining T cell subsets, Langerhans cells, HLA DR antigens, and indirect immunofluorescence. In all, eight nerves were analyzed. 2 of the 8 nerves showed epithelioid cell granulomas surrounded by large numbers of lymphocytes. The predominant lymphocytes in these granulomas were activated T cells expressing CD3 and HLA DR antigens. The proportion of CD3+ and CD4+ cells was higher than that of CD8+ cells. The ratio of CD4+/CD8+ cells in these two biopsy specimens was 5.6 and 1.5, respectively. In these nerves CD4+ cells were diffusely scattered into epithelioid cell granulomas, while CD8+ cells were localized at the periphery of the granuloma. The remaining six nerves showed macrophages containing numerous bacilli, and a few lymphocytes and plasma cells diffusely distributed into the granuloma. In these nerves, only occasional lymphocytes expressing CD3 or CD4 or CD8 and HLA DR antigens were noticed. In two fo the biopsy specimens, a small proportion of CD8+ cells were visualized. Macrophages and Schwann cells were HLA DR+ in all nerves. CD1+ cells were not seen in the infiltrates of any of these nerves. A similar pattern and distribution of cells was noticed in the nerve granulomas of tuberculoid and lepromatous leprosy. These findings suggest that the mechanisms of nerve damage in the patients with neuritic leprosy could be either immunological or non-immunological, depending on the nature and characteristics of the infiltrates.