IFNG and chronic obstructive pulmonary disease: Consistent with intracellular analysis of activated CD4+CD25+ T-cells, IL-4 quantification was significantly decreased in stimulated CD4+ T-cells isolated from COPD patients (p < 0.05), whereas no difference was observed in CD4+ T cell-derived IFN-γ and IL-17A between the different groups (Fig. 2).