CD19⁺ but not CD19⁻ PB and PC are detectable in peripheral blood after vaccination. (A) TT-specific PB, IgG⁺HLA-DR^high PB and IgG⁺HLA-DR^low PC were detected in peripheral blood by flow cytometry as shown (1 week after vaccination) and were analyzed for expression of CD19 in individuals before and at indicated time points after intramuscular vaccination against TetDiph. The analysis shown is representative of 9 individuals immunized with TetDiph vaccine. Numbers of TT-specific PB/mL blood are indicated to illustrate kinetics of the TT-specific PB response. (B) CD19 expression by PB/PC from 4 individuals 1 week after vaccination against 2009 H1N1 influenza with Pandemrix. (C) CD56⁺ PB and PC are absent from peripheral blood before and after vaccination. Representative analyses are shown for circulating PB/PC during steady state (#1 to #4), 1 week after TetDiph vaccination (#5 to #8) and 1 week after Pandemrix vaccination (#9 to #12).