Pathophysiology of cutaneous inflammation.

For the better part of the past century, dermatologists have regarded the skin primarily as a large protective coat. Epidermal keratinocytes were highlighted for their production of keratins and lipids, which contributed to the structural integrity and barrier formation of skin. This "saran-wrap" perspective of skin mentioned keratinocytes only in cutaneous inflammatory reactions as passive targets for damaging diffusion products of infiltrating leukocytes. However, sufficient compelling in vitro and in vivo evidence is rapidly accumulating to support the novel perspective that epidermal keratinocytes can initiate and actively participate in the perpetuation of numerous cutaneous inflammatory reactions that involve a highly diverse array of inciting agents. This presentation emphasizes the keratinocyte and highlights the dynamic immunomodulatory capacity of this overlooked epidermal cell.