Apoptosis in psoriasis.

Apoptosis is a process of programmed cell death that maintains homeostasis of the skin. Apoptotic cell death regulates keratinocyte proliferation and formation of stratum corneum. The process by which keratinocytes undergo apoptosis is a multistep program mediated by binding of specific death ligands to death receptors or by the release of effector cell granules. Dysfunctional apoptosis has an important role in the development of several skin diseases. Psoriasis is a common chronic inflammatory skin disease characterized by hyperproliferation with incomplete differentiation of epidermal keratinocytes and decreased keratinocyte apoptosis. Psoriatic keratinocytes possess an enhanced ability to resist apoptosis, which might be one of the key pathogenetic mechanisms in psoriasis. In addition, psoriasis is nowadays also recognized as the most prevalent autoimmune disease resulting from aberrant activation of both innate and adaptive immunity. However, the role of cell cytotoxicity mediated by cytotoxic CD8+ T cells and NK cells in psoriasis is as yet unclear. Here, we review the role of different apoptotic pathways in psoriasis.