Last reviewed 01/2018

Protective immunity in leprosy is associated with T-cell mediated immunity. A patient with tuberculoid leprosy shows a strong lymphoproliferative response to mitogens and to M. leprae antigens and would have a preponderance of infiltrating CD4 helper/inducer T cells in granulomas, with a few CD8 cells and only an occasional acid-fast bacillus. In lepromatous leprosy the opposite would occur with numerous acid-fast bacilli and negligible T cells in granulomas.

Only a minority of individuals exposed to M. leprae infection develop leprosy because they are able to resist disease by establishing protective immunity. HLA studies have revealed that HLA-DR2 has an association with the development of tuberculoid leprosy. Various other HLA associations are being investigated.