CD28 and chronic obstructive pulmonary disease: Further, studies have reported increased percentages of both CD8+Pgp1+CD28null NKT-like and CD8+Pgp1+CD28+ NKT-like cells in COPD patients when compared to controls while treatment with very low-dose cyclosporine A (Pgp1 inhibitor) combined with standard-dose corticosteroid showed synergistic inhibition of pro-inflammatory cytokines.141