Figure 7. Experimental design to determine antibody secreting plasma cells and recall immune responses.

To evaluate long-lived plasma and memory B cells, groups of mice were intramuscularly vaccinated with a single dose. Six months later a set of the same groups was intramuscularly re-immunized with the same vaccine antigen (Ag) 6 days earlier before sacrifice to determine in vivo recall immune responses (vaccine +/− Ag. rechallenge). In vitro Ag stimulation indicates in vitro antigen exposure with inactivated virus to activate pre-existing memory B cells.