Cathelicidin LL-37 in bronchoalveolar lavage and epithelial lining fluids from COPD patients and healthy individuals.

: Innate immunity is currently under scope of interest concerning its role in the development of chronic obstructive pulmonary disease (COPD). Antimicrobial peptides constitute a potent part of this fast response system. Here, we focus on the role of a specific antimicrobial peptide, the only human cathelicidin, the pleiotropic LL-37 peptide, in the development of COPD under clinical conditions. A cross-sectional study was conducted in groups of 43 patients with COPD (previously classified according to GOLD) and 12 healthy individuals. Bronchoalveolar lavage fluid (BALF) sampling, followed by LL-37 measurements by mass spectrometry combined with previous immunoaffinity purification, was performed. Based on urea levels, concentrations of LL-37 in epithelial lining fluid (ELF) were calculated. Additionally, an antimicrobial assay of growth inhibition of two bacterial species, often involved in COPD development mechanisms, by purchased LL-37 was conducted. Altogether, 55 BALF samples were analyzed. LL-37 levels were significantly higher in BALF from patients in early stages of COPD (GOLD I-II) compared to BALFs from healthy individuals. The same was true for ELF. Cathelicidin’s concentration was significantly lower in both BALF and ELF from patients in advanced COPD (GOLD III-IV). The significantly elevated LL-37 levels both in BALF and ELF in patients with COPD at stage GOLD I-II together with reduced levels in advanced (COPD stage III-IV) further supports the innate immunity involvement in COPD pathology and suggests a profound change in non-specific immunity during the disease progression.