Tissue infiltration of CD4(+) T cells plays an important role in the pathogenesis of allergic diseases. T-cell trafficking is mediated by specific chemokines and their receptors. The purpose of this study was to investigate the participation of the chemokines thymus and activation-regulated chemokine (TARC) and cutaneous T cell-attracting chemokine (CTACK) in a large population of patients with allergic diseases. Serum TARC and CTACK levels were measured in 455 patients with allergic disease. Patients were characterized as having atopic dermatitis (AD), allergic asthma, allergic rhinitis, or combinations or as healthy control subjects. Serum TARC and CTACK levels were correlated with disease activity in patients with AD. Furthermore, in 7 patients with AD, serum TARC and CTACK levels were studied after the start of systemic cyclosporin A treatment. Finally, TARC and CTACK localization was checked by immunohistochemistry in lesional skin biopsy specimens of patients with AD. Both TARC and CTACK serum levels in patients with AD were significantly higher than those in healthy control subjects and patients with allergic respiratory disease. Furthermore, serum TARC and CTACK levels significantly correlated with disease activity in patients with AD. Serum TARC levels paralleled clinical improvement in patients treated with cyclosporin A. Immunoreactive TARC was found in infiltrating cells and endothelial cells of the dermis but not in epidermal cells. The serum TARC level is an objective parameter for disease severity specific for AD. Furthermore, it is a promising tool for treatment monitoring.
