Expression of MMP-12 protein in bronchial smooth muscle tissue and cell cultures by immunostaining. Sections from human bronchial samples were prepared (A). Cell cultures were incubated on 8-well chamber slides for 72 hours in the absence (B) or presence (C) of 10 ng/ml IL-1β. Immunostaining was performed to detect MMP-12 expression using a rabbit anti-MMP-12 antibody. The primary antibody was replaced by a normal rabbit immunoglobulin as a negative control (D). Bar = 50 mm. Results are representative from three donors.