Decrease in interleukin-21 in children suffering with severe atopic dermatitis

Background: Atopic dermatitis (AD) is a kind of eczema with an inflammatory, relapsing, non-contagious, and pruritic skin disorder. It is associated with the local infiltration of T helper type 2 (Th2) cells that secrete interleukin (IL)-4 and IL-5. IL-21 is a member of IL-2 family cytokine mainly expressed by activated CD4+ T lymphocytes. Until now, there is no clinical research in the expression of IL-21 in patients with AD. Methods: We analyzed serum levels of total immunoglobulin E (IgE), allergen-specific IgE, and cytokines IL-4, IL-5, IFN-gamma, IL-17, and IL-21 in AD cases and controls. In addition, cytokine levels in the culture supernatants of peripheral blood mononuclear cells stimulated with anti-CD3 and anti-CD28 Abs, phytohemagglutin (PHA), or pokeweed mitogen (PWM) were measured. We also assessed clinical skin severity by Scoring of Atopic Dermatitis (SCORAD) index. Results: Our results showed that serum total IgE in the case group was significantly higher than that of control group (365.449 +/- 52.945 and 39.243 +/- 7.605 IU/ml, respectively). Logistic regression analysis system reveals serum levels of IL-21 and IFN-gamma are significantly correlated. However, IL- 21 and IL-4, IL-21 and IL-5, as well as IL-21 and IL-17 showed no correlation. Conclusion: A significantly decreased level of IL-21 was observed in children suffering with severe AD compared with controls, suggesting that IL-21 may play a role in AD.