Studies have found that in IBD patients, the expression of KLRG1 and CD57 on CD4+ and CD8+ T cells increases, while CD28 expression decreases, indicating T cell exhaustion, with reduced proliferation ability and immune regulatory function (Li H. et al., 2025; Strunk, 2024; Bottois et al., 2020). Here, CD28 is linked to inflammatory bowel disease.