The Antigenic Substances of the Tubercle Bacillus

Abstract

Summary In the filtrates of cultures grown on the synthetic medium of Long, beside the carbohydrate precipitable substance, we can demonstrate the presence of two antigenic substances. They are separated from each other by acid precipitation. Both by the serological reactions and the antibody production these antigens are well differentiated from each other and from the other antigens of the tubercle bacillus. The difference between these two fractions can be observed also concerning the tuberculin reaction in guinea pigs treated with one or the other of these preparations. The acid-precipitable antigen readily forms antibodies in tuberculous animals which are specific toward this antigen. The acid non-precipitable fractions did not form antibodies reacting with the same preparations or with the acid precipitate and concentrated culture medium, but the sera of the majority of the guinea pigs treated with these preparations gave strong reactions with the bacillary emulsion. From the observations that neither of the two antigens separated by acid precipitation or their mixture gave a positive reaction with several sera produced with the concentrated culture medium and that the latter did not react with the sera produced with the acid precipitate we draw the conclusion that in the culture medium the antigens which are separated by acid precipitation are united in a higher complex which has a specificity markedly different from that of the isolated antigens, and in the reactions of which the effect of the isolated antigens does not appear. The differences which we found concerning the serological reactions between the culture filtrate of different tubercle bacillus strains are probably caused not by the absence or presence of a certain antigen, but by the differences in the way in which the acid-precipitable part is united to the higher complex. Probably the above mentioned complex antigen is responsible for the production of antibodies by the concentrated culture medium and the acid filtrate, although this complex often gives no, or gives only a slight, reaction with these sera.