Mouse lungs were inflated with 10% formalin and embedded in paraffin. Formalin-fixed paraffin-embedded tissue samples were cut into 5-m sections, mounted on slides (Starfrost Plus; Maenzel Glaeser, Braunschweig, Germany), and hydrated using an alcohol gradient. Slides were rinsed in distilled water, followed by antigen unmasking using a 10ϫ concentrated retrieval solution (antigen decloaker solution; Biocare Medical Inc., Concord, CA) according to the manufacturer's instructions, and rinsed in PBS for 5 minutes. For detection of human laminin A1, tissue sections were blocked with H 2 O 2 blocking reagent for 10 minutes at room temperature. Slides were treated with a protein-blocking solution for 10 minutes at room temperature, rinsed, and incubated with human anti-laminin monoclonal antibody (L8271, clone LAM 89; Sigma Aldrich Corp., St Louis, MO) at a titer of 1:1000 for 30 minutes at room temperature, followed by anti-mouse horseradish peroxidase (EnVision FLEXϩ autostainer kit; Daco A/S, Glostrup, Denmark). Slides were rinsed and treated using the mouse-on-mouse polymer kit (MM510; Biocare Medical Inc.) for 30 minutes at room temperature. Laminin staining was detected using a betazoid diaminobenzidine kit (Biocare Medical Inc.). Human tonsil tissue stained with anti-laminin monoclonal antibody was used as positive control, and the same tissue stained only with the secondary anti-mouse horseradish peroxidase served as the negative control.