CD19 and infection: Analysis of CD19+ B cells using theproliferation-tracking dye CFSE at different days after infection indicated thati) proliferating cells appeared at day 3 (Fig.2A), ii) between days 3 and 4 there were always cells that haddivided more than once or even twice in 24h, and iii) at later days postinfection cells appeared to proliferate at a slower rate as judged by the lesspronounced shift of the CFSE profile to the left.