To investigate whether and how increased T-cell responsiveness to IL-2 may predispose to colonic inflammation, T-cell infiltration and activation were compared in colonic tissue resected from the patient with the IL2RA duplication and from eight pediatric-onset treatment-resistant IBD patients (four UC patients, four Crohn’s disease (CD) patients, denoted as “PIBD resection controls”). Here, IL2 is linked to Crohn disease.