Significant elevation of serum levels of eotaxin-3/CCL26, but not of eotaxin-2/CCL24, in patients with atopic dermatitis: serum eotaxin-3/CCL26 levels reflect the disease activity of atopic dermatitis

Atopic dermatitis (AD) is a chronic and relapsing inflammatory skin disease characterized by the predominant infiltration of T cells, eosinophils and macrophages in lesional skin. Recently, eotaxin-2/CCL24 and eotaxin-3/CCL26 were identified as CC chemokines that signal exclusively via the CCR3 receptor and have eosinophil-selective chemoattractant activity, as does eotaxin/CCL11. We previously reported that serum levels of thymus and activation-regulated chemokine (TARC)/CCL17 and macrophage-derived chemokine (MDC)/CCL22 were correlated with the severity of AD. In this report, we investigated the participation of eotaxin-2/CCL24 and eotaxin-3/CCL26 in AD, first measuring the serum levels of eotaxin-2/CCL24 and eotaxin-3/CCL26 in 30 patients with AD, 20 patients with psoriasis vulgaris and 20 healthy controls. The serum levels of eotaxin-3/CCL26 (but not eotaxin-2/CCL24) were significantly higher in patients with AD than in either healthy controls or patients with psoriasis vulgaris; furthermore, the eotaxin-3/CCL26 levels in patients with moderate and severe AD were significantly higher than eotaxin-3/CCL26 levels in patients with mild AD. The serum eotaxin-3/CCL26 levels tended to decrease after treatment, but there was no significant difference between groups. Moreover, the serum eotaxin-3/CCL26 levels were significantly correlated with the serum TARC/CCL17 and MDC/CCL22 levels, eosinophil numbers in peripheral blood and the scoring AD (SCORAD) index. Our study strongly suggests that serum levels of eotaxin-3/CCL26, but not of eotaxin-2/CCL24, have a notable correlation with disease activity of AD and that eotaxin-3/CCL26, as well as TARC/CCL17 and MDC/CCL22, may be involved in the pathogenesis of AD.