Cytokines and chemokines in the epidermis.

Keratinocytes (KC) produce a vast repertoire of cytokines, including interleukins, growth factors, colony stimulating factors, and chemokines. Under normal conditions, most of them are not synthesized or remain in the cytoplasm, but external stimuli, such as trauma, bacterial infections, chemical substances, or ultraviolet irradiation induce the production and release of these cytokines from KC. KC-derived cytokines regulate the immune and inflammatory responses through their receptors on KC, Langerhans cells, dermal fibroblasts and endothelial cells, and infiltrating T-cells.