In contrast to the limited differences of CVID- and APDS-derived B cells concerning basal activation, BCR-mediated phosphorylation of AKT and mTOR in APDS the patients’ CD21pos B cells was significantly increased compared to HD as well as CVID patients’ CD21pos and CD21low B cells (Figure 5B and Supplementary Figure S5). Here, BCR is linked to common variable immunodeficiency.