Serum measurement of interleukin-31 (IL-31) in paediatric atopic dermatitis: elevated levels correlate with severity scoring

Background Interleukin-31 (IL-31) is a novel T-helper-lymphocyte-derived cytokine that plays an important role in human T-cell-mediated skin diseases. When overexpressed in transgenic mice, IL-31 induces severe pruritus resembling eczema in humans. Serum IL-31 was previously found overexpressed in adults with atopic dermatitis (AD). The novelty of this study is the use of a pediatric patient group as well as comparison of IL-31 levels during flare and quiescence. Objective This case-controlled longitudinal study was designed to determine the levels of IL-31 in serum of AD children and its associations in relation to disease activity and severity. Methods Sera were obtained from 50 AD children and 40 healthy volunteers. IL-31 levels were measured using a sandwich ELISA. All AD patients were followed up and re-sampled for serum IL-31 after clinical remission. Serum IL-31 levels were correlated with AD disease activity and severity variables. Results Serum IL-31 levels were significantly higher whether during AD flare [ median, 1600; mean (SD) = 1457.8 +/- 770.4 pg/mL] or quiescence (1040; 958.7 +/- 419.5 pg/mL), than those in controls (220; 197.3 +/- 91.9 pg/mL). Serum IL-31 levels were significantly higher in the high disease severity group compared with the moderate or low severity group. Moreover, serum IL-31 levels correlated positively with the calculated severity scores (LSS, SSS and SCORAD index). Conclusion The results of this study confirm the importance of IL-31 in AD pathophysiology. Serum IL-31 level is an objective reliable marker of AD severity in children. It may represent a novel target for antipruritic drug development.