More than 25 years of accumulating evidence strongly implicates the immune system in the pathogenesis of psoriasis, including both acquired immunity (T cells) and innate host defense (macrophages, antigen-presenting cells, and keratinocytes). Psoriasis also has a strong genetic component, but the identity of the genes involved has largely remained obscure. In a study recently published in Nature Genetics,1 these 2 themes of psoriasis—genetics and immunology—come together in a coherent and clinically relevant way.