Granulomas Induced by Mycobacterium leprae.

Leprosy, a chronic infectious disease caused by Mycobacterium leprae, affects primarily the skin, mucous membranes, and peripheral nerves. It is characterized by a spectrum of symptoms, largely a result of the immunological response of the host to the antigens of M. leprae. At one pole [lepromatous leprosy (LL)] there is an enormous growth of the bacilli in the tissues resulting from a specific and profound lack of cell-mediated immunity (CMI) of the host to M. leprae. At the opposite pole [tuberculoid leprosy (TT)], patients are responsive to M. leprae antigens, and there are few bacilli present in the lesions. A variety of techniques have been applied in the analyses of leprosy granulomas, from standard histological examination to molecular immunological probes. Each technique provides a limited, yet distinctive, look into the constitution of the granuloma. Together, they offer a comprehensive view into the regulation of leprosy granuloma development.