Sustained T-cell reactivity to Mycobacterium tuberculosis specific antigens in 'split-anergic' leprosy

Split anergy represented by delayed-type hypersensitivity skin reaction to tuberculin, but not to leprosin, is known to occur in a distinct proportion of leprosy patients. The mechanism was originally attributed to Mycobacterium leprae-specific suppression of T cells toward common mycobacterial antigens. This study ascertained an alternative explanation, attributing the phenomenon to selective responsiveness to M. tuberculosis-specific epitopes. Indeed, the results of blood T-cell proliferative responses in 11 split-anergic patients showed normal responsiveness to the M. tuberculosis-specific 38 kDa lipoprotein and peptide 71-91 of the 16 kDa antigen but diminished responsiveness to 2 common mycobacterial antigens, represented by the 65 kDa heat shock protein and the fibronectin-binding Ag85 complex, as compared with leprosin responsive patients and healthy contacts. These findings support the hypothesis that split anergy is due to selective recognition of M. tuberculosis-specific epitopes and deletion of T cells reacting to shared mycobacterial antigens.