However, in patients with COPD, effector T-cells are not only suppressed by Tregs but also exhibit an exhausted phenotype with upregulation of programmed death-1 (PD-1) protein, a negative co-stimulatory molecule that impairs immunity by inducing apoptosis, increasing IL-10 production, preventing T-cell proliferation, and reducing T-cell reactivity [90]. This evidence concerns the gene IL10 and chronic obstructive pulmonary disease.