Keratinocytes and cytokine/growth factors.

Cytokines are polypeptide growth factors produced by most nucleated cells in the body, including epithelial cells, keratinocytes, and Langerhans cells in the skin. Cytokines can be classified into interleukins, tumor necrosis factors, chemokines, colony-stimulating factor, interferons, and growth factors. Like classic hormones, cytokines bind to specific receptors to transmit their messages to target cells. Cytokine receptors can be divided into three cytokine receptor superfamilies: the immunoglobulin superfamily, the hematopoietin family, and the tumor necrosis factor family. Following cytokine/cytokine-receptor binding (first messenger), a signal transduction pathway is initiated. Factors affecting homeostasis in the skin and oral mucosa include a delicate balance between cytokines/cytokine-receptors and their antagonists. An imbalance in these variables can influence the development of cutaneous and oral diseases-such as lichen planus, autoimmune disorders, and some neoplastic processes- and can affect wound healing. Potential uses of cytokines include cancer and antiviral therapy.