Evaluation of Cellular Immune Response against Purified Antigen 85 in Patients with Tuberculosis

Background: Tuberculosis (TB) remains an important health problem throughout the world. Despite its significance in public health, mechanisms of protective immunity against Mycobacyerium Tuberculosis in humans have not yet been understood. Objective: To evaluate cell mediated immune response against purified Ag 85, PPD and Phytohemagglutinin (PHA) in patients with tuberculosis and healthy tuberculin positive and negative individuals. Methods: Thirty patients with tuberculosis and 60 healthy tuberculin skin test positive and negative volunteers were participated in this study. Cell mediated immunity was assessed by measuring [³H]-thymidine uptake and detection of IFN-γ in the culture supernatant using commercial ELISA test. Results: In the present study, we showed that IFN- γ production and cell proliferation response to Ag 85 were significantly higher in tuberculin positive than tuberculin negative individuals (P<0.01). Among tuberculous patients, IFN-γ production and cell proliferative responses to Ag 85 was significantly lower in contrast to healthy tuberculin positive individuals (P<0.01). In addition, IFN- γ response in patients with cavitary tuberculosis was lower than patients without cavitation (P<0.05). Conclusion: Based on the higher cell mediated immune responses to Ag 85 in healthy tuberculin positive volunteers compared to patients (especially with advanced disease), purified Ag 85 can be used as a sensitive marker for analysis of immune responses in tuberculosis