Isolation, Purification, and Characterization of Extracellular Antigens of Mycobacterium Tuberculosis1

As amply shown by Dr. Seibert and other workers (1, 2), filtrates of unheated cultures of Mycobacterium tuberculosis contain a variety of protein components, and for many years the extracellular protein has been the subject of extensive investigation, particularly in relation to tuberculin activity. However, even at present very little is known about the fundamental immunochemical properties of these extracellular protein components, such as their antigenic constitution and specificity. Precise knowledge with regard to these properties would undoubtedly be of great importance for a better understanding of the significance of the antigen in the serology and immunology of tuberculous infection. To obtain this information, attempts have been made in our laboratory during the past few years to identify, isolate, and purify the antigen by methods involving the least chemical alteration of the material (3, 4). In this paper, we would like, first, to describe the fractionation procedures by which we have recently obtained two major extracellular antigens (a and /3) of a virulent (H37Rv) strain of tubercle bacilli in highly purified forms, and also to provide some information on the immunochemical properties and the distribution of the antigens in various mycobacteria.