B cell−extrinsic elevation of circulating plasmablasts and increase in IgE isotype switching in the patient. (A) Flow plots of main B cell subsets (top row) and antigen-experienced B cell subsets (bottom row) in one healthy control (left panels) and the patient (right panels). Representative of two independent analyses. (Data shown in rows 1 and 2, column 1 are identical to data in Fig. S5 A, row 1, column 4 and 5.) (B) Gate frequencies for antigen-experienced B cell subsets of five healthy controls (HCs) and the patient. Representative of two independent analyses. (C) Fraction of IgE class-switched cells among antigen-experienced B cell subsets of three healthy controls and the patient. The individual points for healthy control and patient represent one each of three sampling methods (conventional Ficoll prep, separator tubes, and whole-blood RBC lysis) from one experiment. (D) Schematic overview of iGB culture setup (created with BioRender). (E) Cell counts for one representative of two similar experiments. (F) IgM, IgG1, IgG3, and IgE secretion in cultures, normalized to cell count. Full gating strategies are shown in Fig. S5. Statistics were calculated using the unpaired t test. * = P < 0.05. aMBC_PC, aMBC/plasma cell; DN, double-negative; MBC_only, conventional memory B cell; SWmem, switched memory; T1, T2, T3, transitional 1, 2, 3 subsets.