MPO and gastritis: Knockout of gene associated with retinoid–IFN–induced mortality 19 (GRIM-19) led to spontaneous gastritis and SPEM, accompanied by robust inflammation primarily involving CD45+ leukocytes, myeloperoxidase (MPO)+ cells, F4/80+ macrophages, an upregulation of M1-like macrophages, and a decline in anti-inflammatory M2 phenotypes—suggesting a pro-inflammatory microenvironment conducive to disease progression (Zeng et al., 2023).