CD28 and chronic obstructive pulmonary disease: Flow cytometry analysis of anti-CD3/CD28-activated CD4+CD25+ T-cells showed that the proportion of CD4+CD25+ T-cells expressing intracellular IL-4 was significantly lower in COPD patients than in controls (26.3 ± 2.4% vs 35.3 ± 3.4% respectively, p < 0.05), whereas no significant difference was observed in CD4+ T cells-derived intracellular IFN-γ (8.5 ± 0.8% in controls vs 9.2 ± 2.4% in COPD patients) and IL-17A (0.15 ± 0.07% in controls vs 0.18 ± 0.1% in COPD patients) expression (Fig. 1).