Bronchoalveolar lavage procollagen-III-peptide in recent onset hypersensitivity pneumonitis: correlation with extracellular matrix components

Hypersensitivity pneumonitis (HP) is characterized by the accumulation of inflammatory cells in the lung parenchyma, and may progress to fibrosis. The content of the fibroblast derived collagen metabolite procollagen-III-peptide (PCP-III) in bronchoalveolar lavage (BAL) fluid of HP patients has been found to be increased. Previous studies have shown elevation of the fibroblast adhesion molecules, vitronectin and fibronectin in the BAL fluid of recent onset HP. In view of these observations, it was hypothesized that increases in PCP-III would be associated with increases in vitronectin and fibronectin in the BAL fluid of subjects with untreated recent onset HP. BAL was performed in 14 patients with HP and nine normal controls. The aminoterminal domain of PCP-III was measured by radioimmunoassay, and vitronectin and fibronectin by enzyme-linked immunosorbent assay. Detectable amounts of BAL PCP-III were seen in all HP patients but not in the normal controls (mean +/- SEM 5.1 +/- 1.2 versus < 0.2 ng.ml-1; i.e. below the limit of detection of the PCP-III assay). The BAL fluid concentration of PCP-III correlated well with the amount of vitronectin (r = 0.638) and fibronectin (r = 0.710). Except for PCP-III and mast cells, no significant correlations were found between PCP-III, vitronectin, fibronectin and the cellular parameters. The findings suggest that an increased turnover of collagens and proteoglycans is present in the lower respiratory tract of patients with recent onset HP, possibly reflecting remodelling of the extracellular matrix.