CD4 and chronic obstructive pulmonary disease: COPD in its stable phase is characterized by airway inflammation that is central to the pathogenesis of the disease,5 with increased numbers of airway mucosal monocytes/macrophages, CD4+ and CD8+ T and B lymphocytes, and neutrophils that are associated with the severity of airflow limitation.10, 6, 7, 8, 9 Neutrophilic inflammation has been a classical hallmark of both stable COPD8,11 and naturally occurring COPD exacerbations.12