IL-31 serum protein and tissue mRNA levels in patients with atopic dermatitis

Background: Severe pruritus is the primary symptom in atopic dermatitis (AD). Recently, the novel cytokine IL-31 has been implicated in the itching associated with AD. Objective: We performed this study to determine whether IL-31 serum levels are elevated in AD patients and to better characterize the relationship between serum IL-31 level and other established laboratory parameters. Methods: We recruited 55 AD patients, 34 with allergic type AD and 21 with non-allergic type AD, and 38 healthy, non-atopic controls. We checked the laboratory values, severity score, and serum IL-31 levels in all patients and controls, and IL-31 mRNA levels in lesion skin were measured in 13 subjects with AD and in four controls. Results: AD patients displayed significantly higher levels of serum IL-31 that were associated with serum IgE, disease severity, and subjective itch intensity. In AD patients, IL-31 mRNA levels from the lesional skin samples also correlated with serum IL-31 level. Conclusion: IL-31 is likely one of the many mediators inducing inflammation and pruritus in AD. Although our limited sample size prevents us from making any definitive conclusions, our data demonstrate a strong correlation between IL-31 mRNA level and serum IL-31 protein level, which has never been reported before. Moreover, we found correlations between serum IL-31 level and serum IgE, eosinophil cationic protein, disease severity, and subject itch intensity in certain degrees in AD patients.