We hypothesized that Pgp1 may play a role in steroid resistance and would be increased in peripheral blood T, NKT-like and NK cells in patients with COPD, and that this would be accompanied by increased expression of IFNγ, TNFα and granzyme B. We further hypothesized that treatment with low dose cyclosporine A, a Pgp1 inhibitor, would render cells more sensitive to treatment with corticosteroids. This evidence concerns the gene GZMB and chronic obstructive pulmonary disease.