Inflammatory cell profiles and T-lymphocyte subsets in chronic obstructive pulmonary disease and severe persistent asthma

Background Severe persistent asthma (SPA) and chronic obstructive pulmonary disease (COPD) are both associated with non-reversible airflow limitation and airway neutrophilia. Objective To compare inflammatory cell profiles and T lymphocyte subsets between SPA and COPD patients with similar severity of airflow limitation. Methods Sputum induction and lung function tests were performed in 15 COPD patients aged (mean+/-SD) 68+/-8 years, ex-smokers, mean forced expiratory volume in 1 s (FEV1) 45% of predicted (%pred) and 13 SPA aged 55+/-10 years, non-smokers, mean FEV1 49%pred. All patients were on inhaled steroid treatment. Eight asthmatics exhibited irreversible airflow limitation. Differential cell count, metachromatic cell count and double immunocytochemistry for the analysis of T lymphocyte subsets were performed on sputum slides. Results COPD patients had increased sputum neutrophils in comparison with SPA (P<0.03), but similar to SPA with fixed obstruction. In COPD sputum neutrophils negatively correlated with the lung transfer factor for carbon monoxide (K-CO) (r=-0.462, P=0.04). SPA showed significantly increased eosinophils and metachromatic cells vs. COPD patients (P<0.04, P<0.007, respectively). Increased CD4/CD8 and decreased CD4-IFN-gamma/CD4-IL4(+) cell ratio (P<0.001) were found in SPA vs. COPD. In SPA, CD4/CD8(+) cell ratio correlated with sputum eosinophils (r=0.567, P=0.04). Conclusion In spite of treatment with inhaled steroids, SPA and COPD exhibit distinct sputum inflammatory cell patterns, although SPA with fixed airflow limitation and COPD patients have similar numbers of neutrophils.