Morphology and phenotype of CD27⁺ B cells in STAT3_MUT individuals resemble normal memory B cells. (A–C) PBMCs from normal donors and patients with AD-HIES caused by mutations in STAT3 were stained with mAbs specific for CD20, CD27, and CD23, CD24, CD80, CD86, CD95, or TACI. The forward scatter (FSC) and 90° light/side scatter (SSC) and surface expression of the indicated molecules on CD27⁻ (naive) and CD27⁺ (memory) B cells were determined. The histograms in A and B are from a representative normal donor and patient, respectively, whereas the graphs in C depict the geometric mean fluorescence intensity (MFI) of each of the indicated cellular features for CD27⁻ naive (N) and CD27⁺ memory (M) B cells from 3–12 normal donors and STAT3_MUT patients. Each value represents an individual donor or patient; the horizontal lines correspond to the mean. Because of the large difference in the level of expression of CD23 on normal versus STAT3_MUT naive and memory B cells, individual graphs are depicted for normal and patient B cell subsets. *, P < 0.05; **, P < 0.01; ***, P < 0.001.