Perforin expression and cytotoxic activity of sputum CD8+ lymphocytes in patients with COPD

Background: Previous studies have shown that the inflammatory response to cigarette smoking differs between smokers who acquire COPD and those who do not, and the CD8(+) T-lymphocytes have been identified as a key player in this response. Objective: To investigate the cytotoxic activity and perforin expression of CD8(+) lymphocytes in the airway lumen of patients with COPD. Methods: Thirty-six male smokers with COPD, 25 male smokers without COPD, and 10 healthy nonsmokers participated in the study. T-lymphocytes of induced sputum samples were labeled with appropriate monoclonal antibodies and measured using flow cytometry. The cytotoxic activity of CD8(+) cells was defined by incubating them with specific target cells (K562). Results: The percentage and the total number of CD8(+) lymphocytes were significantly higher in COPD smokers compared to non-COPD smokers (p = 0.01 and p = 0.005, respectively) or to healthy nonsmokers (p = 0.02 and p = 0.01, respectively). Perforin expression in CD8(+) cells was significantly higher in smokers with COPD compared to the other two groups (p = 0.001). Increased cytotoxic activity of T cells was also observed in induced sputum of patients with COPD in comparison to the other two groups. Conclusion: CD8(+) cells are not only increased in number in sputum samples of smokers with COPD but are highly activated, expressing high levels of perforin. These findings suggest that CD8(+) T-lymphocytes play a significant role in the inflammatory process of COPD.