Serology of tuberculosis. II. Measurement of antibodies to Mycobacterium tuberculosis by a passive haemagglutination test in human tuberculosis

Analysis of circulating immune complexes (CIC) in tuberculosis: levels of specific antibody and antigens in CIC and relationship with serum antibody

Eighty sera from tuberculosis (TB) patients, 16 Indian and 10 American control sera were analyzed by ELISA for relative titres of antibody against mycobacterial antigens. Levels of specific antibody and mycobacterial Ag in circulating immune complexes (CIC) isolated from these sera were also studied. All these parameters were found to be elevated in TB sera as compared to control sera. Maximum increase was however noted in CIC specific antibody titres. A good correlation was observed between serum and CIC levels of specific antibody (r = 0.72) and between specific antigen (Ag) and antibody (Ab) levels within CIC (r = 0.64). In a few of the TB sera examined, CIC specific Ab contributed less than 1% to the Ab titres in sera. In order to examine the differences between different subgroups within TB patients, a statistical analysis of variance was performed. Sex of the patients had no effect on any parameter. Sputum-positive patients had significantly higher levels of CIC Ag and Ab than the sputum-negative patients, although no significant difference occurred in respect to serum Ab. All three parameters were significantly higher in patients on chemotherapy as compared to fresh untreated cases. The relevance of these observations to the development of a CIC-based immunodiagnostic assay for TB is discussed.

Studies on the efficiency of absorbed bovine PPD in tuberculin and serological tests

The passive haemagglutination, enzyme-linked immunosorbent assay and indirect fluorescent antibody tests were applied to study the non-specific reactions in experimentally infected guinea pigs and tuberculin positive bovines. These cross-reactions were greatly decreased after absorption of either sera with avian PPD or bovine PPD antigen with anti-avian PPD serum. The use of both absorbed sera and antigen raised the specificity of PHA and ELISA to 100%. The use of absorbed sera rendered the IFA specific in 95%. The absorption has reduced the sensitivity of ELISA, IFA and PHA by 14, 27 and 29%, respectively.

Serology of tuberculosis. III. Crossed immunoelectrophoretic analysis of sera from tuberculosis and leprosy patients with antigens from BCG

Sera from tuberculous and leprous patients have been examined for antibody reactivities against components of BCG sonicate (BCGS) antigen. A crossed immunoelectrophoresis with intermediate gel reference system was used in which more than 40 components of BCGS could be identified. Forty (74.1%) out of 54 tuberculous sera and 68 (90.7%) out of 75 leprous sera reacted with at least 1 component of BCGS. While tuberculous sera reacted with 9 distinct components of BCGS, leprous sera reacted with at least 12. Components of BCGS precipitated by tuberculous sera were not specific as they were also precipitated by leprous sera. Overall, non-specific antibody responses were found to be dominant among tuberculous sera and by comparison, the reactivity of leprous sera with BCGS components was of a higher magnitude. Among tuberculous sera, precipitating activity was maximal among those taken from chronic treated cases with relapse followed by those obtained from treated and untreated new cases. Some components of BCGS to which both tuberculous and leprous sera showed strong reactivity have been characterized. It is concluded that immunoprecipitation methods with BCG derived antigens are not useful for the detection of a specific antibody response in tuberculosis or for discrimination between tuberculosis and leprosy.