MPB 64 Possesses Tuberculosis‐Complex'‐Specific B‐ and T‐Cell Epitopes

We have developed monoclonal antibodies (MoAb) reactive with a protein from Mycobacterium tuberculosis of apparent molecular mass 24 kDa, This protein was shown lo he identical with MPB M (Harboe et al., [1]), The MoAb bound to four different epitopes of which two were restricted to the tuberculosis complex” and two were also found in mycobacteria not belonging to the “tuberculosis complex”, The cross‐reactive MoAb demonstrate that MPB M is present in more mycobacterial species than previously assumed. MPB 64 was show n lo induce strong delayed type hypersensitivity (Dth) reactions in out bred guinea pigs immunized with M tuberculosis and M. hovis bacille Calmette‐Guérin (BCG), No reaction was observed m animals immunized with mycobacteria not belonging to the “tuberculosis complex”, The Dth‐inducing capacity of MPB 64 was compared with that of another 24 kDa protein purified from W. merciless and of the previously described 38 kDa protein. The Dth responses lo these three antigens were further analysed in four inbred guinea pig strains. A genetic restriction of the ability of the animals to respond to MPB 64 as well as to the 38 kDa protein was observed.