Antigen-specific IFN-γ responses correlate with the activity of M. tuberculosis infection but are not associated with the severity of tuberculosis disease

Ifn-γ is a key cytokine in antituberculosis (tb) defense. however,how the levels of its secretion affect m. tuberculosis (mtb) infection is not clear. we have analyzed associations between ifn-γ responses measured in quantiferon®-tb gold in-tube (qft) assay,tb disease severity,and mtb infection activity. tb severity was evaluated based on the results of radiological,microbiological,and clinical examinations. antigen-driven ifn-γ secretion did not correlate with tb severity. mitogen-induced ifn-γ secretion correlated inversely with the form of pulmonary pathology and the area of affected pulmonary tissue; the levels of spontaneous ifn-γ secretion correlated with patients' age (r = 0.395,p = 0.001). mtb 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-γ secretion increased in a row: patients with residual tb lesions < patients with low tb activity < patients with high tb activity. thus,antigen-driven ifn-γ secretion and qft results did not associate with tb severity but associated with the infection activity. the results suggest that quantitative parameters of ifn-γ secretion play a minor role in determining the course of tb disease but mirror the activity of the infectious process. © 2016 irina yu. nikitina et al.