TNF and psoriasis: In IL-23-induced psoriasis and in Imiquimod-induced psoriasis (a model based on the observation that patients treated with Aldara cream experience flares of psoriasis (108), which most closely match gene expression found in psoriatic skin (109)), the critical DC are TNF-α and IL-1β-producing monocyte-derived DC, including a population of inflammatory Langerhans cells.