The role of macrophages in the lymphoproliferative response to Mycobacterium leprae in vitro.

Peripheral blood lymphocytes from patients suffering from lepromatous leprosy do not normally react in vitro to stimulation by Mycobacterium leprae antigens. In contrast, we found that T cells from non-responding patients in combination with macrophages from responding patients or healthy contacts did respond well to M. leprae. Conversely, T cells from responding patients or healthy contacts in combinations with macrophages from non-responding patients failed to respond. It seems, therefore, that the lack of response normally observed in in vitro tests using cells from lepromatous leprosy patients is due to a failure of their macrophages to present M. leprae antigens in an immunogenic form.