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.