SIGNIFICANCE OF CIRCULATING IMMUNE-COMPLEXES IN PULMONARY TUBERCULOSIS

Google Scholar
  • 1 January 1984
    • journal article
    • research article
    • Vol. 58  (2) , 317-324
Abstract
In the present study attempts were made to demonstrate circulating immune complexes (CIC) in sera from patients with pulmonary tuberculosis (TB) by 3 techniques; latex agglutination; 3.5% PEG [polyethylene glycol] precipitation and determination of optical density at 280 nm and RIA [radioimmunoassay] of CIC using bovine spermatozoa. About 40 normal control sera and 100 TB patients sera were investigated for the presence of CIC. Seventeen per cents of the cases of pulmonary TB were positive by latex agglutination while none of the control was positive. Levels of CIC as detected by PEG precipitation and RIA were significantly elevated in patients as compared to normal controls. While IgG, IgA and IgM were elevated in the CIC of patients, IgM Ig were detected only in patients and not in controls. Detection of CIC may at times by useful in diagnosis, prognosis and therapeutic monitoring of disease processes, but it is the characterization of immune complexes (IC) and identification of the specific components of these complexes which holds the greatest potential for better understanding of disease mechanisms. CIC were precipitated using 3.5% PEG from sera of patients suffering from TB. The specific anti-TB antibody component of complex was determined using Staphylococcus aureus protein A as a solid phase, anti-BCG antibody and 125I-labeled TB antigen. The specific TB antigen component of the IC was dissociated thermally from TB antibody and assayed by a radioimmunoassay technique developed in the laboratory. Patients were classified into 2 groups. Those whose sputum was positive for Mycobacterium tuberculosis by smear and or culture and those whose sputum was negative. The TB antigen concentrations of CIC was higher 19.1 .+-. 2.3 ng/ml (mean + s.e.) in sputum positive cases, and 9.9 .+-. 1.9 ng/ml in sputum negative cases as compared to 2.2 .+-. 0.3 ng/ml in controls. Patient groups were significantly different from controls as well as from each other (P < 0.001). Anti-TB antibody ratios were 11.7 .+-. 1.48, 5.1 .+-. 1.5 and 0.6 .+-. 0.1 in sputum positive, sputum negative and controls. The significance of differences between the groups was P < 0.001. The effect of treatment administered over a period of 12 wk or more was evaluated. It was observed that in patients with persistent demonstration of M. tuberculosis in the sputum, the TB antigen and TB antibody levels of CIC were consistently high. In patients who responded to anti-tubercular drugs the TB antigen levels decreased progressively while TB antibody levels remained high. These studies indicate that isolation and identification of specific antigen and antibody is not only useful in the separation of diseased groups from normal but is useful in evaluating therapeutic responsiveness and progress of disease.