Secreted IgM and IgG in response to CD40L and IL-21-Fc. Percentage of plasmablasts after in vitro stimulation with CD40L and IL-21-Fc correlates with secretion of (A) IgM and (B) IgG in the supernatant. IgM and IgG secretion from patients post-HSCT were analyzed according to conditioning (C-D), donor B-cell chimerism (E-F), Ig replacement status (G-H), and response to tetanus vaccine (I-J). Control patients were combined from healthy adults and children. Medians and interquartile ranges are indicated. Brackets depict comparisons with significant P values: *P < .05; **P < .01; ***P < .001; and **** P < .0001.