Human IL-23 is primarily produced by antigen-presenting cells and induces and maintains differentiation of Th17 cells and Th22 cells, a primary cellular source of proinflammatory cytokines such as IL-17 and IL-22, which mediate the epidermal hyperplasia, keratinocyte immune activation and tissue inflammation inherent in psoriasis.
Tyk2(-/-) mice when injected with IL-23 showed significantly reduced ear skin swelling with epidermal hyperplasia and inflammatory cell infiltration compared with wild-type mice.