Mucosal immune response to cholera toxin in ageing rats. I. Antibody and antibody-containing cell response.

Although ageing is accompanied by systemic immunodeficiencies, the status of the mucosal immune system in the elderly remains unresolved. The gastrointestinal mucosal immune response was evaluated in young, mature and old male rats subjected to intra-intestinal immunization with cholera toxin (CTx). Five days following secondary immunization, the alpha-CTx-IgA titre in the bile of immunized rats was markedly reduced, i.e. the values measured in young rats were approximately five-fold higher than those of old animals. alpha-CTx-IgA levels in non-immunized rats were negligible and age-related shifts in other antibody titres (alpha-CTx IgG and IgM) were not significant. The antibody response to CTx was not reflected in the total IgA content of the samples. The number of alpha-CTx antibody-containing cells (ACCs) in the small intestinal lamina propria was significantly reduced in old immunized rats in comparison with the young or mature animals. These data suggest that ageing compromises both non-immune cell (antibody transport by hepatocytes) and immune cell (number of ACCs in the gut wall) functions in response to cholera toxin immunization in this animal model.