IL1RL1 and inflammatory bowel disease: Similarly, an increase in IL1RL1 levels in the gut, mainly associated with the active state of UC, has been described, together with elevated circulating levels of IL1RL1 and IL-33 in IBD patients [28], [29]; Pastorelli et al. also showed that anti-TNF therapy modulated IL1RL1 and IL-33 serum levels, increasing the soluble isoform of IL1RL1, making more decoy receptors available, and reducing circulating IL-33 [29].