PRF1 and chronic obstructive pulmonary disease: Our group has reported increased production of Th1 pro-inflammatory cytokines IFN-γ and TNF-α by CD8+ T cells in both peripheral blood and lungs [11] and higher levels of the cytotoxic mediators granzyme b and perforin in peripheral blood NKT-like and NK cells in adult inflammatory lung disease including chronic obstructive pulmonary disease (COPD), severe asthma and bronchiolitis obliterans syndrome following lung transplantation [12–15].