Chronic generation of IgA⁺ plasmablasts in steady state is not affected by a systemic tetanus/diphtheria vaccination. (A) Cytometric detection of blood plasmablasts/plasma cells expressing intracellular IgA, IgG, or IgM. (B) Proportions of icIgA⁺, icIgG⁺, and icIgM⁺ cells among total blood icIg^high cells before and 7 days after tetanus/diphtheria vaccination. Blood donors had frequencies of antibody-secreting cells among PBMCs of 0.08% to 0.45% before and 0.42% to 1.31% after vaccination. (C) Frequencies of cells expressing icIgA, icIgG, or icIgM among PBMCs before and 7 days after vaccination.