Common antigen of Mycobacterium leprae, M. lepraemurium, M. avium, and M. fortuitum in comparative studies using two different types of antisera.

No. 21 mycobacterial antigens of Mycobacterium lepraemurium, M. avium, M. fortuitum, and M. leprae were compared in crossed immunoelectrophoresis using two different antibody sources, a serum pool from lepromatous leprosy patients (LSII) and a rabbit anti-M. smegmatis antiserum. M. lepraemurium, like M. avium, was found to contain the 21 A and 21 C determinants. M. fortuitum contained in addition a new type of determinant, 21 D.M. leprae antigen no. 21 carried the A as well as the B dertminants, the latter found so far only in the leprosy bacillus. The separate taxonomic position of M. leprae, suggested by earlier studies of the no. 21 antigen, is further supported by the present results, which also demonstrate the potential use of submolecular heterogeneity for such investigations.