Background: Previous studies have shown that the inflammatory response to cigarette smoking differs between smokers who develop chronic obstructive pulmonary disease (COPD) and those who do not and that the CD8+ T-lymphocytes have been identified as a key player in this process. The aim of this study was to investigate further the role of CD8+ cells and their subtypes in sputum cells.
Methods: Sputum induction was performed in 36 COPD patients, 25 smokers without COPD and 10 non-smoking healthy controls. After stimulation of sputum lymphocytes with phorbol-myristate-acetate, we used double immunocytochemical methods to identify CD4+, CD8+ cells and CD8+ INFgamma or IL4 cells (Tc1,Tc2).
Results: COPD patients had an increased number of CD8+ cells in sputum as compared with smokers without COPD (P = 0.0001) and control subjects (P = 0.001). CD8+-IL4 cells were reduced both in COPD and in smokers without COPD compared to controls (P = 0.0001), while CD8+-IFNgamma cells were significantly reduced only in COPD (P = 0.001) as compared with controls. A significant (P = 0.02) relationship between the CD8+-IL4/CD8+-IFNgamma ratio and FEV1 (% pred) was found only in COPD patients.
Conclusion: These findings suggest that an imbalance both in T-lymphocyte subpopulation (CD4/CD8) and in CD8+ cell subsets (Tc1/Tc2) characterizes the inflammatory responses of smokers with established COPD.