Notably, Schmitz et al. also identified IL-33 as the ligand for the previously orphan receptor suppression of tumorigenicity 2 (T1/ST2) (also called interleukin 1 receptor-like 1), which had already been associated with allergic disease; indeed, IL-33 injection into mice led to increased spleen weight, IgE, type 2 cytokines, mucus production by epithelial cells, and significant eosinophilia. Here, IL33 is linked to allergic disease.