Steady-state plasmablasts/plasma cells express β₇ integrin and the mucosal chemokine receptor CCR10, whereas vaccination-induced, antigen-specific plasmablasts express CD62L. (A) Expression of β₇ integrin and CD62L of total intracellular Ig^high plasmablasts/plasma cells and antigen-specific plasmablasts from peripheral blood was assessed cytometrically before and 7 days after vaccination. The contribution of β₇ integrin⁺, CD62L⁺, and β₇-integrin⁻/CD62L⁻ plasmablasts/plasma cells was analyzed in steady state and 7 days after tetanus/diphtheria vaccination relatively (B) and in absolute numbers (C). (D-F) Steady-state CD19⁺/CD27^high plasmablasts/plasma cells were stained for CCR10 (open histogram) or with control mAb, staining 3% (± 1%) of the same cells (shaded histogram). In steady state, surface IgA and CCR10 were coexpressed on CD19⁺/CD27^high plasmablasts/plasma cells, whereas vaccination-induced plasmablasts specific for rTT.C did not express CCR10 (96% were CCR10⁻, 2 donors), and the frequency of total CCR10⁺ plasmablasts/plasma cells was lower than in steady state. (G) Peripheral blood CD19⁺/CD27^high/CD20^low plasmablasts/plasma cells in steady state were stained simultaneously for surface IgA, CCR10, and β₇ integrin (open histograms) or controls (shaded). A representative analysis of 1 of 5 blood samples is shown.