Airway Surfactant Protein D Deficiency in Adults With Severe Asthma

Background Surfactant protein D (SP-D) is an essential component of the innate immune defense against pathogens within the airways. SP-D also regulates allergic inflammation and promotes the removal of apoptotic cells. SP-D dysregulation is evident in several pulmonary diseases. Our aim was to investigate whether airway and serum levels of SP-D are altered in treatment-resistant severe asthma. Methods SP-D concentrations were measured in matched serum and BAL samples collected from 10 healthy control subjects (HC) and 50 patients with asthma (22 with mild asthma [MA] and 28 with severe asthma [SA]). These samples were also evaluated by using Western blot analysis to investigate variations in SP-D size. Results SP-D levels in BAL samples were significantly lower in SA compared with HC and MA ( P P P P Conclusions These findings suggest defective innate immunity within the airways in SA, as reflected by low BAL SP-D concentrations and altered bacterial presence with airway neutrophilia. Furthermore, BAL SP-D leakage into the serum in patients with SA may provide a peripheral blood biomarker, reflecting increased epithelial damage and/or epithelial permeability within the peripheral airways.