Intestinal lymphocyte number, migration and antibody secretion in young and old rats.

This study demonstrates that the mucosal immune response to cholera toxin (CT) is compromised in old rats in comparison with young animals. The total number of immunoglobulin A (IgA)-secreting cells is similar or higher in the intestinal inductor and effector sites in old animals. However, the number of specifically induced anti-CT IgA antibody-secreting cells is lower in these tissues in comparison with those in young animals. The kinetics of this immune response in the different gut-associated lymphoid tissues studied suggests that the age-associated decline in the number of anti-CT IgA-secreting cells in the intestinal mucosa reflects impaired IgA immunoblast migration. Our data from lymphocyte adoptive transfer studies indicate that factors intrinsic to both the donor cells and the host recipient influence the migration of immunoblasts from the Peyer's patches to the effector site. For example, donor cells from old donors transferred to either young or old recipient rats migrate slower than young donor lymphocytes transferred into old host animals. In vitro studies clearly indicate that ageing does not impair antibody secretion by intestinal mucosal plasma cells. Therefore, the age-related decline in the intestinal mucosal immune response, e.g. diminished specific antibody titres in intestinal lavage, reflects fewer antibody-secreting cells in the mucosa.