Antigen-Specific IFN- Responses Correlate with the Activity of Infection but Are Not Associated with the Severity of Tuberculosis Disease.

IFN- is a key cytokine in antituberculosis (TB) defense. However, how the levels of its secretion affect () infection is not clear. We have analyzed associations between IFN- responses measured in QuantiFERON®-TB Gold In-tube (QFT) assay, TB disease severity, and infection activity. TB severity was evaluated based on the results of radiological, microbiological, and clinical examinations. Antigen-driven IFN- secretion did not correlate with TB severity. Mitogen-induced IFN- secretion correlated inversely with the form of pulmonary pathology and the area of affected pulmonary tissue; the levels of spontaneous IFN- secretion correlated with patients' age ( = 0.395, = 0.001). infection activity was evaluated based on radiological data of lung tissue infiltration, destruction, dissemination or calcification, and condensation. The rate of positive QFT results and the levels of antigen-driven IFN- secretion increased in a row: patients with residual TB lesions < patients with low TB activity < patients with high TB activity. Thus, antigen-driven IFN- secretion and QFT results did not associate with TB severity but associated with the infection activity. The results suggest that quantitative parameters of IFN- secretion play a minor role in determining the course of TB disease but mirror the activity of the infectious process.