Comparative analysis of whole-blood interferon-γ and flow cytometry assays for detecting post-treatment immune responses in patients with active tuberculosis.

Background: Intracellular cytokine flow cytometry (ICCFC) has been explored to detect tuberculosis (TB) infections; however, there are little data regarding its use to examine the dynamic responses of Mycobacterium tuberculosis (MTB)-specific T-cells after anti-tuberculous therapy. The aim of the present study was to analyze both dynamic changes in functional MTB antigen-specific T-cell subsets and interferon-gamma (IFN-γ) levels using ICCFC and the QuantiFERON-TB Gold In-Tube (QFT-IT) test, respectively, following anti-tuberculous treatment in patients with active TB.
Methods: Twenty-six patients with active TB were enrolled in the study, and QFT-IT and ICCFC were performed simultaneously both before and after treatment. IFN-γ levels (QFT-IT test) and the numbers of IFN-γ- or tumor necrosis factor-alpha (TNF-α)-expressing T-cells (ICCFC assay) were examined after stimulation with MTB antigen.
Results: There was no significant reduction in the mean IFN-γ concentrations measured by the QFT-IT test after anti-tuberculous treatment (p=0.314). ICCFC analysis showed that the numbers of IFN-γ+ /CD4- T-cells and CD4+ T-cells producing TNF-α, either alone or in combination with IFN-γ, were significantly reduced after anti-tuberculous treatment. The IFN-γ+ /TNF-α+ /CD4+ T-cell subset showed the greatest difference between untreated and treated patients with active TB (area under the curve = 0.734, p=0.004). Conclusions: Unlike the QFT-IT test, ICCFC provides diverse immunological information about dynamic changes in the number of MTB antigen-specific T-cells following anti-tuberculous therapy. Thus, analysis of MTB antigen-stimulated T-cell responses using ICCFC might have a role to play in monitoring treatment responses in patients with active TB. © 2013 Clinical Cytometry Society.