• MackayRose-Marie ARMClinical and Experimental Sciences, University of Southampton Faculty of Medicine, Southampton General Hospital, Southampton, UK. Electronic address: r.a.mackay@soton.ac.uk., Christopher L Grainge, Laurie C Lau, Clair Barber, Howard W Clark, and Peter H Howarth.
• Clinical and Experimental Sciences, University of Southampton Faculty of Medicine, Southampton General Hospital, Southampton, UK. Electronic address: r.a.mackay@soton.ac.uk.
• Chest. 2016 May 1; 149 (5): 1165-72.

BackgroundSurfactant 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.MethodsSP-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.ResultsSP-D levels in BAL samples were significantly lower in SA compared with HC and MA (P < .001) and inversely correlated with BAL eosinophil cationic protein concentrations in SA (P < .01). Serum SP-D was significantly increased in SA compared with HC and MA (P < .001), and BAL/serum ratios were significantly lower in SA compared with HC and MA (P < .001). Reduced SP-D levels in BAL samples, with concomitant increases in serum in SA, were associated with degraded fragments of SP-D in the serum and increased BAL neutrophil counts and lipopolysaccharide levels.ConclusionsThese 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.Copyright © 2016 American College of Chest Physicians. Published by Elsevier Inc. All rights reserved.

52 keywords...

hide…