Bronchoalveolar lavage (BAL) fluid was obtained from 24 sequentially studied patients with adult respiratory distress syndrome (ARDS) for assessment of potential activating and mediating factors. Proteolytic activity of the fluids was observed by measuring cleavage of radiolabeled proteins of the contact (Hageman factor) and complement systems. Proteolytic activity was observed in 17 of 24 (71%) patients with ARDS, and BAL fluid of the 7 ARDS patients without demonstrable, active, enzyme exhibited inhibitory activity for the proteolytic activity. The enzymes cleaved Hageman factor, prekallikrein, plasminogen, high molecular weight kininogen, C4, C3, C5, and Factor B of the complement system. Cleavage of the contact system proteins producted fragments similar or identical in size to the fragments observed during activation of these molecules, although continued incubation invariably reduced the protein to small peptide fragments. None of 7 normal individuals, and 29 of 99 patients (29%) with other forms of pulmonary disease contained measurable enzymes.
William W. Mcguire, Roger G. Spragg, Allen B. Cohen, Charles G. Cochrane