Interaction between mesothelial cells and macrophages in the initial process of pleural adhesion: ultrastructural studies using adhesion molecules.

Detachment of mesothelial cells is an early step in adhesion of the human pleura. To elucidate this process, we used adhesion molecules as the targets of primary antibody and performed immunohistochemical staining of the mesothelial cells that cover the surface of the sites of pleural adhesion and the macrophages that migrate from connective tissue. The surface of the adhesion site that was formed as a result of edematous and villiform elongation of the connective tissue underlying the visceral pleura was covered with mesothelial cells. However, there was partial detachment of the mesothelial cells caused by adherence to macrophages that had migrated from within the connective tissue, and that adherence was mediated by adhesion molecules. We demonstrated that both mesothelial cells and macrophages each express both CD54 and CD11a, important adhesion molecules. It was surmised that the detachment of the mesothelial cells is the result of interaction with the macrophages via those adhesion molecules and that over time it progresses to pleural adhesion.