RESUMO
The classification used for leprosy so far distinguishes between two polar forms (pauci-bacillary and multi-bacillary), with different influences on the immune cells. The identification of specific antigens of the germ surface with monoclonal antibodies allows finer differentiation in classification, which now extends to transitional forms of clinical relevance. The current status of knowledge about immunological phenomena triggered by Mycobacterium leprae is complex, and controversy is rife at present. The bacillus is comparable to other mycobacteria in antigenicity. Owing to the complicated composition of the cellular envelope, few epitopes are accessible for immunological reactions. Investigation on the behaviour of T-lymphocytes in combination with analysis of the bacterial surface structures led to the development of a new pathogenetic concept. In spite of different immunological and inflammatory reactions in patients (reflecting the individual pathology), the discrimination between a partial and a total immunological defect is made. So far, no histocompatibility-antigen type has been found that allows recognition of the predisposition to infection. Immunity against the bacteria is achieved after BCG in some cases. All this suggests that the development of a vaccine via biotechnical synthesis of idiotypes and anti-idiotypes may be possible.