A Study of Antigens Active in the Tannic Acid Hemagglutination Test Present in Filtrates of Culture of Mycobacterium Tuberculosis

A number of different fractions from culture filtrates of Mycobacterium tuberculosis have been tested for ability to sensitize tanned red cells to agglutination by rabbit antiserum prepared against phenol-killed tubercle bacilli. The different fractions varied considerably in their potency in this respect, and some were inactive. The antigenic relationship of the fractions active in the test was studied in cross inhibition tests. Four active fractions from unheated culture filtrates were found to be completely distinct from each other serologically and showed very little cross reaction. Three preparations of PPD and other fractions from heated culture filtrates cross reacted with each other strongly and little difference could be seen among them. These heated fractions also cross reacted with one of the unheated preparations (that analogous to Seibert's C protein).