T-cell blast activation in presence or absence of leniolisib. Peripheral blood mononuclear cells (PBMCs) from healthy subjects (n = 4) or APDS patients (n = 3) with the indicated p110δ mutation were activated with anti-CD3 and anti-CD28 (1 μg/mL each) and maintained in culture media containing IL-2 to generate T-cell blasts. (A) After 30 minutes of preincubation with a dimethyl sulfoxide (DMSO) vehicle control or the indicated concentration of leniolisib, cells were stimulated for 10 minutes with anti-CD3 or were left unstimulated. Then, cells were fixed and stained for intracellular levels of AKT phosphorylated on S473 or S6 phosphorylated on S240/244. A representative healthy subject is shown in panel A. Quantification of cumulative data for median fluorescence intensity (MFI) of pAKT (B) and pS6 (C) stains is shown. The patient with E525K mutation corresponds to study patient 1.