Antimicrobial peptides are markers of inflammation of Community-Acquired Pneumonia (CAP)

Antimicrobial peptides (AMP) are components of airway secretions and contribute to the innate host defense system of the lung. In the respiratory tract, epithelial cells as well as professional immune cells such as neutrophils and macrophages secrete AMPs. It was the aim of this study to examine the concentrations of the cathelicidin LL-37/hCAP-18 and the β-defensin hBD-2 in sputum, pharyngeal washings, and bronchoalveolar lavage fluids (BALF) of patients with community-acquired pneumonia (CAP). The material used for this study was obtained from 107 patients recruited by the CAPNETZ (German Community Acquired Pneumonia Network). AMP concentrations were measured by ELISA and western-blot analysis. It is shown that LL-37/hCAP-18 and hBD-2 levels are increased in sputum and BALF of CAP patients. LL-37/hCAP-18 concentrations positively correlate with other laboratory parameters (C-reactive protein, levels of total and unsegmented leucocytes). Furthermore, current or former smoking was associated with significantly reduced hBD-2 levels in sputum and pharyngeal washing fluid of CAP patients. Together, this data shows that AMPs are markers of inflammation during CAP and that cigarette smoke inhibits the expression of these important host defence factors during CAP.