At one day post inoculation, IL-17A–neutralizing antibody dampened, whereas rm–IL-17A protein augmented the expression of proinflammatory genes of IL-1β, IL-18, TNF-α, CXCL1, CXCL15 and MMP-9 in response to P. aeruginosa infection in COPD mouse lungs. The gene discussed is MMP9; the disease is chronic obstructive pulmonary disease.