Non-neoplastic mucosa (non-NM) in CVID-patients displayed prominent lymphocytic gastritis (100%) and a dysfunctional immune microenvironment, characterised by higher rates of CD4+/CD8+/Foxp3+/GATA3+/PD-L1+ immune cells and the expected paucity of CD20+ B-lymphocytes and CD138+ plasma cells, when compared to non-CVID patients (p < 0.05). Here, FOXP3 is linked to common variable immunodeficiency.