Abnormal B-cell differentiation in TPP2 deficiency. (A-B) Human CD19⁺ B cells were analyzed for expression of differentiation and senescence markers. The proportion of CD11c⁺CD21⁻ ABCs was compared between the patient (P1), 8 adult controls (HD), 5 untreated ALPS-FAS patients, and pediatric patients with autoimmune cytopenia and lymphoproliferation in the context of CVID. Patient B cells were analyzed for T-bet expression. (C) The proportions of CD11b⁺ and CD11b/c+ double-positive splenic CD19⁺ B cells were determined in 6- to 12-month-old TPP2 knockout (KO) and WT mice (n = 4). The experiment was repeated twice with similar results.