Keratinocytes in allergic skin diseases

The aim of the review is to provide up-to-date information on the multiple roles of epidermal keratinocytes in the immune reactions associated with allergic contact dermatitis and atopic dermatitis skin diseases.In the last two decades, it has become clear that keratinocytes are highly active immunological cells, with major control over the acute and the chronic phases of skin inflammation by means of cytokine/chemokine production and surface molecule expression. Keratinocyte responses in skin allergic reactions are rather disease-specific and keratinocytes from genetically determined skin disorders, including atopic dermatitis, show intrinsic abnormalities in their capacity to respond to trigger factors.Lymphokines and cytokines released by T lymphocytes and other immune cells represent the most important stimuli that elicit the inflammatory activation of keratinocytes. Depending on the type and extent of T-cell infiltrate present in allergic contact dermatitis and atopic dermatitis skin lesions, keratinocytes are exposed to different cytokine micromilieu and, in turn, produce flogosis mediators qualitatively and quantitatively specific for each disease. Keratinocyte-derived inflammatory molecules amplificate skin immune responses associated with allergic contact dermatitis and atopic dermatitis, and contribute to the disease process and clinical phenotype development.