Role of the immune system and immunological circuits in psoriasis.

Psoriasis vulgaris is a chronic skin disease in which our understanding of the pathogenesis has substantially grown in recent years. Our current appreciation of the role of the immune system is that it plays a necessary and driving role in the disease process. Investigations into the genetics of psoriasis has spurred further examinations into the contributions of immune mediators such as IL-23, IL-17, IL-22, and TNF as well as cellular mediators including a variety of dendritic cell populations of the skin and the growing number of T cell types, including the Th17 and Th22 subsets. Investigations into how these soluble and cellular elements interact with each other and the skin and form complex signal circuits to engender the psoriasis phenotype is starting to become elucidated. Furthermore, these recent advances have been fruitful in leading to the development of new classes of biologic therapeutics that are remarkably effective in halting the disease process.