Maintenance of long-term immunological memory by Ig+CD45R+ non-plasma B cells following mucosal immunizations

To determine whether long-term immunological B cell memory following mucosal vaccinations is maintained by terminally differentiated Ig−CD45R− plasma cells or Ig+CD45R+ B cells, we immunized mice orally with the non-toxic B subunit of cholera toxin (CTB) as a carrier protein haptenated with FITC (CTB-FITC) plus CT adjuvant. We found that the adoptive transfer of Ig+CD45R+ but not the Ig−CD45R− cells, resulted in higher numbers of FITC-specific IgA-secreting cells in the intestine as well as higher anti-FITC serum IgA titers, suggesting that long term B cell immunological memory following oral vaccinations preferentially resided within the Ig+CD45R+ B cell population.