Leprosy provides a useful model for understanding immunoregulatory mechanisms in man 1 since its clinical and histopathological manifestations vary according to the patient’s immune responsiveness to Mycobacterium leprae. Thus far, leprosy research has yielded insight into the molecular and cellular basis of T cell-mediated resistance and unresponsiveness to infectious pathogens, the roles of cytokines and γδ T cells, and the dynamic immune events associated with acute changes in the clinical manifestations of disease.