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Interaction of keratinocytes with infiltrating lymphocytes in allergic eczematous skin diseases

Purpose of review Eczematous skin diseases, including atopic dermatitis, are characterized by T-cell infiltration into the epidermal compartment. Whereas an active role of the main constituents of the epidermis, the keratinocytes, has long been neglected, it has become clear in the last decade that they are important, immunological active cells. This review highlights the recent work published between March 2005 and May 2006 that expands our knowledge about keratinocyte–T-cell interactions in epidermal immune responses, with emphasis on the pathogenesis of eczematous skin diseases in humans, mainly atopic dermatitis. Recent findings The cross-talk between T cells and keratinocytes is only partially understood. Recent studies suggest that in certain micromilieu settings, keratinocytes are capable of regulating the response of CD4+, CD8+ as well as regulatory T cells. Keratinocytes, however, respond to T helper type 1 and type 2-derived mediators which often exert synergistic effects on these cells. So far, only very few studies have investigated how T-cell–keratinocyte interaction influences the outcome of inflammatory responses in autologous human systems. Summary Keratinocytes play an active part during the acute and the chronic phase of eczema by means of cytokine production and surface molecule expression which leads to an inflammatory infiltrate in the upper layers of the skin.