A local mucosal immunological memory that could be efficiently triggered to protective antibody formation on renewed
antigen exposure might account for the several-year long protection against
reinfection and disease seen in individuals after
cholera disease. The duration and other functional aspects of gut mucosal immunological memory to the
cholera toxin (CT), which is the key pathogenic factor in
cholera, were examined in mice. Six months or even 2 years after an initial series of oral immunizations with CT a single repeat oral exposure to CT in submicrogram amounts evoked a brisk
IgA antitoxin response in the lamina propria. A three-fold increase in
IgA antitoxin-producing cells (SFC) was evident within 16 h, with a further rise in SFC numbers over the next several days. The anamnestic gut mucosal
IgA antitoxin response was associated with a substantial increase in protection against challenge of intestinal loops with CT. The rapid increase in
IgA antitoxin SFC in the gut is believed to reflect memory cells dispersed in the gut mucosa which can be rapidly triggered into
antitoxin formation by
antigen encounter in vivo and such cells could clearly be responsible for the long-term immunity seen after
cholera disease or oral vaccination.