Detection of plasma kallikrein in the bronchoalveolar lavage fluid of asthmatic subjects and its origin

Plasma kallikrein was detected in bronchoalveolar lavage fluid (BALF) obtained from bronchial asthma patients and compared to that of normal adults. Characterization using chromogenic substrates S-2302, S-2266, S-2222, and using inhibitors SBTI, Trasyrol, DIFP, suggested that the amidolytic activity in BALF from bronchial asthma patients was compatible with plasma kallikrein. Using immunoblotting method with specific antibody, we concluded that the plasma kallikrein-like activity in BALF was surely plasma kallikrein itself. The plasma kallikrein activity in BALF obtained from patients with late asthmatic response (LAR) was significantly higher than that in fluid from patients with immediate asthmatic response (IAR). Kininogenase activity was also detected by cleavage of bradykinin from acid-treated plasma. To investigate whether the plasma kallikrein in BALF originated from human lung mast cell or basophil, the supernatant of lung mast cells and that of basophils were tested using three chromogenic substrates and the immunoblotting method. We conculuded that the plasma kallikrein in BALF did not originate from lung mast cells or basophils. These results suggested that elevated amounts of plasma kallikrein in BALF of patients with LAR might contribute to the pathogenesis and modification of LAR.

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