Identification of human β-defensin-2 in respiratory tract and plasma and its increase in bacterial pneumonia

Human beta-defensin-2 (hBD-2), a novel antimicrobial peptide, was originally isolated from human skin, We found that synthetic hBD-2 has high bactericidal activity against Escherichia coli under conditions nearly the same as in human bronchial airway surface liquid. We prepared an antiserum against hBD-2 and established a highly sensitive radioimmunoassay (RIA). Reverse-phase high-performance liquid chromatography coupled with the RIA showed that hBD-2 is present in human lung, bronchoalveolar lavage fluid, and plasma. The plasma concentration of hBD-2 in patients with bacterial pneumonia was 32.1 +/- 3.7 fmol/ml (mean +/- SE), 3.9-fold that of normal individuals. By reverse transcription-polymerase chain reaction, the hBD-2 gene transcript was detected in the respiratory epithelial surface of the human lung, Human p-defensin-a seems to function in airway mucosal defense. Our findings provide a clue to elucidate its pathophysiological significance in respiratory infection. (C) 1998 Academic Press.