CD28 and inflammatory bowel disease: CD8 (+) Tregs play a key role in mucosal tolerance, with CD8 (+) CD28 (−) Treg cells preventing experimental colitis in mice and an increased proportion of CD8 (+) CD28 (−) Treg cells in the blood of colitis mice treated with mesalazine (Ceeraz et al., 2021; Ménager-Marcq et al., 2006).Traditional treatments for IBD mainly involve nonbiological therapies such as aminosalicylates, thiopurines, and steroids (Burger and Travis, 2011).