Specificity of Mycobacterium tuberculosis antigen 5 determined with mouse monoclonal antibodies.

Four mouse monoclonal antibodies have been developed which react with Mycobacterium tuberculosis antigen 5. Each of these monoclonal antibodies has been used to prepare immunoabsorbents, and antigen has been isolated from unheated M. tuberculosis H37Ra culture filtrate by affinity chromatography with these absorbents. Antigen thus obtained was found to be similar in tuberculin reactivity and in enzyme-linked immunosorbent assays to antigen 5 isolated from polyclonal immunoabsorbents, and the protein yields from the monoclonal immunoabsorbents were similar to those from polyclonal absorbents. Antigen recovered from monoclonal absorbents cross-reacted with antigens of Mycobacterium kansasii in delayed skin tests. Immunoelectrophoresis demonstrated that the major component of the antigens eluted from the monoclonal immunoabsorbents was mycobacterial arabinomannan. Antigen 5 was not identified in the eluates by immunoelectrophoresis. These observations support the hypothesis that antigen 5 and M. tuberculosis arabinomannan contain a single major shared epitope.