CD8A and chronic obstructive pulmonary disease: In addition, blood CD8/CD28 (null) cells have been found to increase in both current (30 patients, mean age 59 years, FEV1% 57) and ex-smoker (18 patients, mean age 60 years, FEV1% 62) COPD groups, which express significantly higher levels of IFNγ, OX40, 4-1BB, CTLA4, granzyme, and perforin when stimulated than CD8/CD28+ T cells.