PD1/PD-L1 pathway in psoriasis and psoriatic arthritis: a review

Programmed-death 1 (PD-1) is a co-receptor that inhibits the inflammatory response, and thus helps in maintenance of peripheral immunotolerance. Impairment in the PD-1/PD-L1 pathway is believed to play an important role in many immune-mediated diseases, including systemic lupus erythematosus, rheumatoid arthritis, systemic sclerosis and au-toimmune hepatitis, and, as emphasized recently, in psoriasis and psoriatic arthritis. Biologic drugs targeting immune checkpoint regulators may be associated with new-onset psoriasis or exacerbations of pre-existing dermatosis. In this review we discuss the role of PD-1/PD-L1 pathway in psoriasis basing on data published to date.