MMP's and PE but not HNE underlie PGP generation by COPD sputum. Inhibitors of MMP-1, MMP-9, PE and HNE and azithromycin, a macrolide antibiotic, were included in the assay of PGP generation by COPD sputum. MMP inhibitors were used at 50 μM, PE inhibitor and azithromycin at 100 μM and HNE inhibitor at 1 μM. MMP-1, MMP-9 and PE inhibitors and azithromycin reduced PGP generation by COPD sputum whereas inhibition of HNE had no effect. Experiments were performed twice using pooled sputum from six COPD patients. Results are shown as percent inhibition of PGP production compared to sputum without inhibitors and are presented as mean ± SEM (n = 2).