IL-12-and IL-23 in health and disease.

•IL-12 and IL-23 represent two major cytokines controlling inflammation.•Deregulated levels of IL-23 affect barrier function and will manifest in pathologies of skin, gut and lung.•Inflammatory bowel disease, arthritic disorders and psoriatic skin complaints have all partaken in clinical studies aimed at neutralizing IL-12 and IL-23, with varying degrees of success.•Detailed collection of clinical trials and successful development of treatments aimed at neutralizing members of the IL-12 cytokine family are discussed.