Increased expression of CD208 (DC-LAMP) in epidermal keratinocytes of psoriatic lesions

Psoriasis is a chronic inflammatory skin disease characterized by epidermal hyperproliferation and infiltration of inflammatory leukocytes. The aim of this study was to clarify the role of innate immunity involving dendritic cells (DC) and keratinocytes in psoriasis. We immunohistochemically examined the expression of DC markers such as CD1a, CD83, CD207 (Langerin), CD208 (DC-LAMP) and CD209 (DC-SIGN) in psoriatic skin and gamma-interferon (IFN-gamma)/12-O-tetradecanoylphorbol-13-acetate (TPA)-stimulated keratinocytes in vitro. CD208 was strongly expressed in basal and suprabasal layer keratinocytes in addition to DC in the perivascular lesions of the psoriatic dermis. Furthermore, the enhanced expression of CD208 in the perinuclear lesions of IFN-gamma-/TPA-stimulated keratinocytes was observed in vitro. Because a defect of the granular layer in psoriatic lesions has been recognized, increased expression of lysosome-related CD208 in the basal and suprabasal keratinocytes of psoriatic lesions might represent aberrant epidermal differentiation. Additionally, these CD208-positive keratinocytes possessing putative antigen-processing activity might play a key role as antigen-presenting cells in psoriatic skin.