TYK2 and Autoimmunity: As a critical intracellular component of the IL12, IL23 and type I IFN cytokine cascades, TYK2 plays pivotal roles in autoimmune disorders including psoriasis (Ps), inflammatory bowel disease (IBD), systemic lupus erythematosus (SLE), lupus nephritis, multiple sclerosis (MS), etc. (2–4, 8, 22, 25).