Consequently, the cells that may be affected by PD-1 inhibitors such as dendritic cells, T helper cells, and Treg cells are characterized by their ability to secrete cytokines including interferon-gamma, IL-1, IL-17, and IL-22 [242,243] and thereby play an important role in the pathogenesis of both new-onset psoriasis and reactivated psoriasis [243,244]. Here, PDCD1 is linked to psoriasis.