Figure 2.

Collagenase-3 gene expression in silicotic lungs predominates from fibroblastic cells adjacent to granuloma-infiltrating macrophages. Experimental lung silicosis was induced in adult rats as described in Materials and Methods, and lungs were harvested 7 d after treatment. (A) Immunohistochemistry for macrophages using the antibody clone ED1. (B) In situ hybridization for collagenase-3 mRNA. (C and D) Dual in situ hybridization and immunohistochemistry for collagenase-3 and macrophages. Immunohistochemistry for macrophages using the antibody clone ED1 (A) and in situ hybridization for collagenase-3 (B) on serial tissue sections reveal that granuloma-infiltrating macrophages (arrows) are abundant at sites of collagenase-3 gene expression (white grains). Dual in situ hybridization and immunohistochemistry for collagenase-3 and macrophages (C and D) show that the hybridization signal for collagenase-3 mRNA (black grains) is predominantly associated with fibroblastic cells adjacent to macrophages (arrows) and not from the macrophages themselves. Original magnification is 100× for A and B and 1000× for C and D.