Defective peripheral B-cell tolerance checkpoint in IPEX patients. (A) Antibodies from mature naive B cells from a healthy donor and IPEX patients were tested by ELISA for anti-HEp-2 cell reactivity. Dotted lines show ED38-positive control and solid lines show binding for each cloned recombinant antibody. Horizontal lines define cutoff OD₄₀₅ for positive reactivity. For each individual, the frequency of HEp-2–reactive (filled area) and non-HEp-2–reactive (open area) clones is summarized in pie charts, with the total number of clones tested indicated in the centers. The frequencies of (B) HEp-2–reactive and (C) polyreactive mature naive B cells in healthy controls and IPEX patients (left) and their evolution between the new emigrant/transitional and mature naive B-cell compartments (right) are shown. (D) Mature naive B-cell clones from IPEX patients show various patterns of cytoplasmic HEp-2 staining. (E) The frequency of antinuclear clones is low (left) and is not increased between the new emigrant/transitional and mature naive B-cell compartments (right).