Thymus and activation-regulated chemokine in atopic dermatitis: Serum thymus and activation-regulated chemokine level is closely related with diseaseactivity

Background: Atopic dermatitis (AD) is a chronic and relapsing inflammatory skin disease characterized by the predominant infiltration of T(H)2-type ce lls in lesional skin. Thymus and activation-regulated chemokine (TARC/CCL17 ) is a chemokine that attracts CC chemokine receptor 4-positive (CCR4(+)) o r CCR8(+) cells. Objective: The purpose of this study was to investigate the participation o f TARC in AD. Methods: We measured serum TARC levels in 40 patients with AD, 20 healthy c ontrol subjects, and 20 patients with psoriasis. We also examined disease a ctivity by using SCORAD score; serum soluble E-selectin, soluble IL-2 recep tor, IgE, and GM-CSF levels; and eosinophil numbers in peripheral blood, as well as correlations between TARC levels and these factors. The positivity of CCR4 of CD4(+)CD45RO(+) cells in PBMCs was examined by using FAGS analy sis. Immunohistochemical staining of TARC and GM-CSF was performed in the l esional skin of patients with AD. Results: The serum TARC levels of patients with AD were significantly highe r than those of healthy control subjects and patients with psoriasis, The s erum TARC levels significantly correlated with eosinophil number (r = 0.61) , SCORAD score (r = 0.60), and serum soluble E-selectin levels (r = 0.58) a nd weakly correlated with serum soluble IL-2 receptor levels (r = 0.34) in patients with AD. The TARC levels of patients with AD decreased after the t reatment in accordance with the improvement of clinical symptoms. The CCR4 positivity of CD4(+)CD35RO(+) cells in PBMCs of patients with AD was also h igher than that of healthy control subjects. Immunohistochemical staining r evealed that TARC was positive in keratinocytes in the epidermis and in vas cular endothelial cells, T cells, and dendritic cells in the dermis. Conclusion: Serum TARC levels are associated with disease activity of AD, a nd TARC may play an important role in the pathogenesis of AD.