ERAP1 and colitis: To assess the impact of ERAP1 on neutrophil infiltration during colitis progression, Ly6G+ CD11b+ neutrophils were analyzed in peripheral blood leukocytes (PBLs) and intraepithelial lymphocytes (IELs) of DSS-treated ERAP1 WT and ERAP1+/− mice using flow cytometry.