IL33 and neoplasm: In the resulting ILC2-deficient mice (mice transplanted with RORα−/− BM), we observed that IL-33-expressing primary tumours (TC1) or IL-33 expressing metastatic tumours (A9+IL-33) grew more rapidly and had a higher frequency of metastasis in ILC2-deficient mice, whereas the growth rate of the A9 cells not expressing IL-33 was not found to be significantly different between mice with or without ILC2s (Fig. 4).