Diagnostic value of non-specific humoral immune changes in children investigated for tuberculosis by skin test and bacteriology

It was suggested that repeated skin tests (IDR) used to diagnose childhood tuberculosis (TB) potentially change the immune response of the host. Adaptive cell-mediated immunity is the most important in protection against TB, but there is no information on the changes in the dynamics of immune globulins (Ig) and circulating immune complexes (CIC) in these patients. We hypothesized that the changes would be dependent on both the skin test results and bacteriological (BK) category of the subjects. The study was carried out in three groups of children, 1 to 17 years old, positive to both skin test and bacteriology (IDR+BK+, n=18), positive to the skin test but negative for bacteriology (IDR+BK+, n=12) and negative to skin test, but positive for bacteriology (IDR-BK+, n= 9). Serum samples were subjected to total immunoglobulin (Ig) and immune complexes measurements (CIC), carried out by 0.24% zinc sulphate and 4.2% polyethylene glycol precipitation tests, respectively. Optical densities (optical density units, ODU) were red spectrophotometrically. The statistical significance of the results was estimated by Student's t test. View this table: Table 1-Total Ig and CIC levels of children tested for tuberculosis The highest concentration of immune globulins and circulating immune complexes, statistically significantly different (p<0.05), found in the IDR-BK+ group indicated the dependence of humoral changes on the presence of bacteria, rather than related to IDR, suggesting an added diagnostic value by use of these non-specific serological tests.