Since the role of MMF in AC relies on its capacity to regulate T-cell dysfunction, we evaluated lymphocyte subpopulations before and during the treatment with MMF, since reduced isotype-switched memory B-cells (≤0.55% of B-cells), increased CD21low B-cells (>10%), and reduced T-cells (CD4) have been linked to an increased risk of non-infectious complications in CVID (19, 20). Here, CD4 is linked to common variable immunodeficiency.