IL1RL1 and periodontitis: Although the cells in the PRT express high levels of sST2, the similar phenotypes observed in both Il33Δ/Δ and Il1rl1–/– mice suggest that accelerated bone destruction is due to the lack of IL-33/ST2 signaling and that its function is protective against local acute inflammation in periodontitis (Fig. 5a, b, Supplementary Fig. 21a).