Abstract: The pathogenesis of psoriasis is closely associated with immune system. Most of recent studies have suggested that psoriasis is a mixed Thl/Thl7 immunological disease. Besides dendritic cells, T cells, keratinocytes and Thl type cytokines such as interleukin (IL)-12 and IL-18, Thl7 type cytokines such as IL-23 and IL-22 also participate in the development of psoriasis. Thl7 type immune response may play an essential role in the pathogenesis of psoriasis.