IL1RL1 and neoplasm: We previously demonstrated that CD4+ FOXP3+ Tregs promote tumor progression in the AOM/DSS-induced model of CRC.19 To address the specific role of ST2-expressing Tregs in intestinal tumorigenesis, we next performed a kinetic analysis of colonic ST2+ CD4+ FOXP3+ Tregs, which were found to progressively increase in frequency and transiently upregulate the IL-33 receptor during the course of AOM/DSS treatment (Fig. 2d and Supplementary Fig. 1C, respectively).