Switched memory B cells and in vitro plasmablast generation in patients post-HSCT. Percentage of switched memory B cells (the percentage of CD19⁺ B cells that are IgD⁻ and CD27⁺) and percentage of plasmablasts (the percentage of CD19⁺ B cells that are CD27^high and CD38^high) after in vitro stimulation with CD40L and IL-21-Fc were measured in patients with IL2RG/JAK3 SCID analyzed according to conditioning (A-B), donor B-cell chimerism (C-D), Ig replacement status (E-F), and response to tetanus vaccine (G-H). Control patients were combined from healthy adults and children. Medians and interquartile ranges are shown. Brackets depict comparisons with significant P values: *P < .05; **P < .01; ***P < .001; ****P < .0001.