Interferon gamma response in pulmonary tuberculosis patients in Ile-Ife, Osun State, Nigeria
Serum level of interferon gamma (IFN-γ) in pulmonary tuberculosis (TB) patients was evaluated. The variations in IFN-γ levels with treatment, its association with severity of TB disease and sputum smear grading were also determined. This was with a view to determining the level of IFN-γ in TB patients as compared with apparently healthy individuals. One hundred subjects were selected which included 50 active pulmonary TB patients and 50 matched controls. The patients were followed up for 4 months during treatment with anti-TB drugs. Levels of IFN-γ produced on stimulation with TB antigens were determined using Enzyme-Linked Immunosorbent Assay (ELISA) at zero month and was repeated after 2 and 4 months of treatment. Difference in mean of IFN-γ levels in patients and controls was determined with a student T test. Chi associations and correlations between IFN-γ were also determined. The variation in IFN-γ levels with treatment was assessed using analysis of variance (ANOVA). Regression analysis was used to determine predictive role of baseline IFN-γ in determining treatment outcome. The result showed that the mean level of IFN-γ induced by TB antigens in patients was 1.45±1.02 IU/ml. Actual mean level of IFN-γ in TB patients was 1.41±1.02 IU/ml compared with 0.34±0.39 IU/ml in the control group (p=0.000). The mean level of IFN-γ decreased significantly from 1.41±1.02 IU/ml at baseline to 0.21±0.33 IU/ml at the fourth month of treatment with anti-TB drugs (p=0.000). The baseline mean level of IFN-γ induced by TB antigens was lower in patients that converted to smear negative at 2 months of treatment (1.17±0.87 IU/ml) than in patients that failed to convert (2.08±1.15 IU/ml) (p=0.0005). A similar trend was observed among smear converters and non-converters after 4 months of treatment. The baseline mean level of interferon gamma (IFN-γ) induced by tuberculosis (TB) antigens for patients in severity class III was 1.51 1.04 IU/ml and significantly higher compared with those in class I (0.50 0.63 IU/ml) (p=0.03). The same trend was also observed in patients that had high sputum grade. Positive correlation was observed between mean of baseline IFN-γ and TB severity. There was a significant correlation between sputum smear and sputum smear grade with baseline IFN-γ after 2 months of treatment (p >0.05). Baseline IFN-γ level was predicted by human immunodeficiency virus (HIV) and smoking status of the patients (p 0.05). The study concluded that interferon gamma level was higher in TB patients than in the control group. There was also a significant decline in IFN-γ level with anti-TB treatment and TB patients with higher level of stimulated IFN-γ had severe form of the disease.