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Role of the chemokine receptor CCR4 and its ligand thymus- and activation-regulated chemokine/CCL17 for lymphocyte recruitment in cutaneous lupus erythematosus.

Skin-infiltrating T lymphocytes are thought to play a major role in the pathogenesis of cutaneous lupus erythematosus (CLE). In this study, we investigated the role of the chemokine receptor 4 (CCR4) and its ligand thymus- and activation-regulated chemokine (TARC/CCL17) for the recruitment of T cells in inflamed skin of patients with CLE. We found significant numbers of CCR4+ T lymphocytes in the skin of all patients with CLE. Interestingly, a subset of patients with disseminated scarring skin involvement were characterized by both lesional and circulating CD8+ T cells expressing CCR4. Destruction of epidermal and adnexal structures was histomorphologically associated with CCR4+ cytotoxic T cells invading basal layers of the epidermis where keratinocytes showed apoptotic death. The CCR4 ligand TARC/CCL17 was strongly expressed in skin lesions and elevated in the serum of CLE patients. The functional relevance of lymphocytic CCR4 expression could be confirmed by TARC/CCL17-specific in vitro migration assays. Our investigations suggest that CCR4 and TARC/CCL17 play a role in the pathophysiology of CLE. In particular, cytotoxic CD8+ T cells expressing CCR4 appear to be involved in scarring subtypes of CLE.