• barrier function;
  • dendritic cells;
  • stratum corneum;
  • transepidermal water loss

Abstract: External assault to the skin is followed by an epidermal response including synthesis of DNA, lipids, cytokines and migration of antigen presenting cells. MIP-3α (CCL20, LARC, Exodus-1, Scya20) is a recently described C-C chemokine, predominantly expressed in extralymphoid tissue, which is known to direct migration of dendritic cell precursors and memory lymphocytes to sites of antigen invasion. We assessed the expression of MIP-3α in human skin using semi-quantitative polymerase chain reaction. In vivo, MIP-3α mRNA was constitutively expressed at low levels in untreated human epidermis. After acute disruption of the epidermal permeabiltiy barrier MIP-3α mRNA was upregulated in the epidermal fraction, whereas dermal MIP-3α mRNA levels remained unchanged. In vitro, MIP-3α was increased in cultured keratinocytes treated with IL-1α and TNF-α and was present in immature and mature dendritic cells, THP-1 monocytic cells and activated T cells. Finally, skin biopsies from patients with psoriasis, contact dermatitis and mycosis fungoides showed abundant expression. In biopsies from atopic dermatitis and graft vs. host disease a weak signal was present, whereas no expression was found in scleroderma and toxic epidermal necrolysis. We conclude that regulation of MIP-3α mRNA is part of the epidermal response to external assault. Its upregulation may represent a danger signal for increased immunosurveillance in barrier disrupted skin and inflammatory skin conditions with impaired barrier function to counteract potential antigen invasion.