The first report, which designated IL-33 as a member of the IL-1 superfamily [1], described that injection of IL-33 (0.4 or 4 μg daily) in mice for a short time (up to 7 days) induces splenomegaly, eosinophilia and serum IgE as well as pathological changes in the lung and the digestive tract. Here, IL33 is linked to Splenomegaly.