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

Abstract EN

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.