Local activation of the coagulation and fibrinolysis systems in lung disease

Extravascular coagulation and fibrinolysis is an integral part of inflammatory reactions. Disordered expression of procoagulant and profibrinolytic factors by mononuclear phagocytes of the lung (i.e. lung alveolar macrophages (LAM) and interstitial macrophages) may have important bearings on inflammatory lung tissue destruction and repair. Based on this hypothesis we have measured the presence of trigger molecules and activation products of the coagulation and fibrinolytic system in cell-free bronchoalveolar lavage fluid and in bronchoalveolar cells. Patient groups with chronic obstructive disease (COLD) (n = 76), idiopathic pulmonary fibrosis (IPF) (n = 29), sarcoidosis (n = 22), lung cancer (n = 36), pneumonia (n = 39), acquired immunodeficiency syndrome (AIDS) (n = 17) and a control group (n = 60) were studied by bronchoalveolar lavage (BAL). In all patient groups tissue thromboplastin (TPL) and fibrinopeptide A (FPA) were significantly increased compared to controls. Plasminogen activator (PA) activity was significantly lower in patients than in normals, and usually associated with high levels of antifibrinolytic activity. The level of PA inhibitor (PAI-2) was not significantly higher in any patient group compared to controls. The sensitivity of the method for fibrin degradation products (FDP) analysis was not high enough to detect FDP in BAL fluid of control individuals, whereas such products could be demonstrated in 25-53% of patients in various categories. We conclude that disordered expression of procoagulant and plasminogen activator activities in bronchoalveolar lavage fluid may reflect a milieu that favours accumulation of fibrin in inflammatory lung tissue and form the basis for the development of pulmonary fibrosis.