KLRG1 and ulcerative colitis: In the peritoneum of mice with dextran sulfate sodium (DSS)-induced ulcerative colitis (UC), the expression of miRNA-21a-5p secreted by M1-sEVs was increased, which targeted the expression of the cell adhesion molecule E-cadherin and reduced its binding to killer-cell lectin-like receptor G1 (KLRG1), indirectly promoting the activation of group 2 innate lymphoid cells (ILC2s), which are important components of natural immunity, leading to excessive pathogenic Th2 immunoreaction commonly observed in UC (Lu et al., 2021).