A study of tuberculosis antibodies by bentonite flocculation.

Bentonite particles sensitized with concentrated human Old Tuberculin were used for detection of circulating antibodies to M. tuberculosis in human sera.There was no sharp distinction between the titres of patients with active and inactive tuberculosis, but progressively higher antibody titres accompanied increased severity of infection. The sera of 95.3% of the patients studied had a titre of 1:8 or higher. This level was considered to be the minimal significant titre indicative of the presence of metabolically active bacilli in old and new lesions. Tuberculin-negative controls and syphilitic sera were negative. A common zone of incidence in the 1:8-1:32 range was found where differentiation between tuberculin-positive healthy people and patients with tuberculosis was not possible; however, titres of 1:64 or more were found only in tuberculous patients. The antibody under study is heat-labile.