CD4 and chronic obstructive pulmonary disease: Interestingly, in a longitudinal study involving bronchial biopsies in patients with COPD, the number of sputum neutrophils, lymphocytes, interleukin-8 and eosinophilic-cationic-protein levels significantly increased at 12 months after successful smoking cessation [15], whereas in a cross-sectional study with bronchial biopsies, ex-smokers with COPD had higher CD3+, CD4+, and plasma cell numbers compared to current smokers [16].