Platelet Activating Factor Receptor and Intercellular Adhesion Molecule-1 Expression Increases in the Small Airway Epithelium and Parenchyma of Patients with Idiopathic Pulmonary Fibrosis: Implications for Microbial Pathogenesis.

Background : Idiopathic pulmonary fibrosis (IPF) is an irreversible lung fibrotic disorder of unknown cause. It has been reported that bacterial and viral co-infections exacerbate disease pathogenesis. These pathogens use adhesion molecules such as platelet activating factor receptor (PAFR) and intercellular adhesion molecule-1 (ICAM-1) to gain cellular entry, causing infections. Methods : Immunohistochemical staining was carried out for lung resections from IPF patients (n = 11) and normal controls (n = 12). The quantification of PAFR and ICAM-1 expression is presented as a percentage in the small airway epithelium. Also, type 2 pneumocytes and alveolar macrophages were counted as cells per mm2 of the parenchymal area and presented as a percentage. All image analysis was done using Image Pro Plus 7.0 software. Results : PAFR expression significantly increased in the small airway epithelium ( p < 0.0001), type 2 pneumocytes ( p < 0.0001) and alveolar macrophages ( p < 0.0001) compared to normal controls. Similar trend was observed for ICAM-1 expression in the small airway epithelium ( p < 0.0001), type 2 pneumocytes ( p < 0.0001) and alveolar macrophages ( p < 0.0001) compared to normal controls. Furthermore, the proportion of positively expressed type 2 pneumocytes and alveolar macrophages was higher in IPF than in normal control. Conclusions : This is the first study to show PAFR and ICAM-1 expression in small airway epithelium, type 2 pneumocytes and alveolar macrophages in IPF. These findings could help intervene microbial impact and facilitate management of disease pathogenesis.