Evaluation of the Humoral Immune Response in Pulmonary Tuberculosis Patients

The aim of this study was to evaluate the humoral immune response in the pulmonary tuberculosis patients. A total of 54 patients receiving treatment at the hospital and 41 healthy subjects were included in this study. Bactericidal activities of serum complements were assessed by the colony count method. The total serum immunoglobulin G (IgG) was measured by nephelometric method and complement components C3 and C4 were measured by immunoturbidometric methods. It was found that the patients had very high ESR (85.0 mm h-1) and about 78% of them had BMI<18.5. The bactericidal activity of complement from fresh serum of the patients was similar to that of the control group (p>0.05) but the heat-inactivated serum showed significantly high bactericidal activity (p<0.001). The IgG level was also significantly elevated than that of the controls (p<0.001). There was no difference in the levels of complement protein C3 between the patients and controls but C4 was significantly elevated in the patients (p<0.01). High IgG levels in the patients might have a relationship with enhanced killing of bacteria, which was observed in experiments with heat-inactivated serum. Elevated level of C4 indicated reduced utilization and thereby suppressed activity of the classical complement pathway. The findings suggest that the humoral immune response is altered in the pulmonary tuberculosis patients.