Interestingly, however, when we combined stimulated protein and flow data from both smokers and COPD subjects (total n = 15) (Table S3), there was a significant correlation (rS = 0.55, p = 0.025) between the percentage of CD103+ cells and stimulated production of IFN-γ in vitro by the lung CD4+ T cells of the same individuals (Fig. 3B). This evidence concerns the gene CD4 and chronic obstructive pulmonary disease.