The number of BAL MMP-12+-macrophages was higher in COPD smokers (1.6 ± 0.3 × 106/ml) compared to COPD ex-smokers, 'healthy' smokers and healthy never-smokers (0.9 ± 0.4, 0.4 ± 0.2, 0.2 ± 0.1 × 106/ml respectively, p < 0.05). The gene discussed is MMP12; the disease is chronic obstructive pulmonary disease.