Association of vitamin D and antimicrobial peptide production during late-phase allergic responses in the lung

Summary Background Vitamin D may play important roles in regulating immune responses and in defence against infectious diseases by effects on both innate and adaptive immune responses. Little is known regarding activation of vitamin D within airway tissues and its relationship to inflammation and antimicrobial responses. Objective The objective of this study was to investigate the activation of vitamin D within the airways and to define relationships between vitamin D metabolites and measures of inflammatory and antimicrobial responses assessed by bronchoalveolar lavage (BAL) during late‐phase responses following allergen challenge of allergic subjects. Methods Segmental allergen challenge was performed with saline and allergen in 16 adult allergic subjects. BAL was performed in both saline and allergen‐challenged sites 20–24 h. after challenge. Following extraction from BAL fluids, levels of 25‐hydroxy‐vitamin D (25(OH)D) and 1,25‐dihydroxy‐vitamin D (1,25(OH)2D) were assayed by specific radioimmunoassays. The cleavage product of cathelicidin, LL‐37, was assayed by ELISA. Cellular constituents and albumin were measured. Results Levels of vitamin D metabolites were increased in concentrated BAL fluids after allergen compared to saline challenge. Levels of 1,25(OH)2D increased from largely undetectable to 2.5 pm (median; range: 1–29.5; P = 0.005) while 25(OH)D increased from 3.2 (0.8–6.2) to 6.2 (1.5–184.9) nm (P = 0.0006). Levels of LL‐37 increased from 2.1 (1.4–4.1) to 14.5 (2.2–106.7) ng/mL BAL (P = 0.0005). Levels of LL‐37, 1,25(OH)2D, and 25(OH)D following allergen challenge were correlated with each other (P