Studies of mycobacterial antigens, with special reference to Mycobacterium leprae

Eight individual antigens were detected in soluble antigen preparations from Mycobacterium leprae bacilli by using pools of serum samples from lepromatous leprosy patients as antibody reagents in crossed immunoelectrophoresis. Two of these antigens were analyzed further. Antgent no. 1 gave an elution pattern on Sephadex G-200 corresponding to a molecular weight of 285,000. This antigen was also present in three slow-growing and eight fast-growing mycobacterial species. There was a reaction of complete identity in immunological tests using lepromatous serum pools as well as with rabbit antisera raised against M. leprae and M. smegmatis. Antigen no. 21 of M. leprae showed antigenic heterogeneity when compared with other species. Three types of antigenic determinants were detected; one, called 21A, was shared by all mycobacteria, another, called 21B, was limited to antigen no. 21 of M. leprae; a third, called 21C, was present in all mycobacteria except the leprosy bacillus. This submolecular heterogeneity may indicate a separate taxonomic position of M. leprae among the mycobacteria.