Tuberculous Lymphadenitis: Skin Delayed-Type Hypersensitivity Reaction and Cellular Immune Responses
AbstractBackground: Tuberculous lymphadenitis (TL) is the commonest form of extra-pulmonary tuberculosis in tropical countries.
Objective: This study aimed to characterize in vivo and in vitro cellular immune responses to Mycobacterium PPD in TL patients as markers of disease and healing.
Methods: Following informed consent, 36 TL patients, 40 patients with pulmonary tuberculosis (TB) and 20 apparently healthy individuals were enrolled when they met specific selection criteria. The tuberculin skin test (TST) and peripheral blood mono-nuclear cells (PBMCs) culture were conducted using PPD. The cytokines were measured using commercial kits.
Results: The mean TST was 24.6 ±8.0 mm for TL patients. The TST was variable in pulmonary TB patients and healthy individuals. It was reactive in a third of pulmonary TB patients with a mean of 20 ±3.0 mm and reactive in half of the healthy individuals with a mean of 12.6 ±3.2 mm. Pre and posttreatment interferon gamma (IFN-γ) mean levels were 498.6 ±905.8 pg/ml and 710.0 ±844.6 pg/ml respectively (p=0.0001) for TL patients, while IL-10 mean levels were 93.0 ±136.0 pg/ml and 32.4 ±31.7 pg/ml respectively (p= 0.0001). TST-reactive Pulmonary TB patients had significantly higher IFN-γ (851 ±234.4 pg/ml) compared to TBLNT patients (p = 0.0001), while pulmonary TB patients had significantly lower IL-10 compared to TBLNT patients (p=0.0001). Apparently healthy individuals had significantly lower IFN-γ and IL-10 levels compared to TBLNT and pulmonary TB patients (p=0.003).
Conclusion: Strong TST reactivity, high IFN-γ and IL-10 levels are good surrogate markers of active TBLNT, while increasing IFN-γ levels and decreasing IL-10 levels mark healing. Tuberculosis Skin Test reactivity although a good diagnostic marker does not disappear with treatment.