Reduced immunological responsiveness induced by oral immunization in nude mice.

Nude mice (Nu-Nu) were immunized orally by intragastric administration of sheep red blood cells (SRBC) repeated daily for 4 days. This oral immunization resulted in the appearance in the animals serum of anti-SRBC antibodies and of IgA Plaque Forming Cells (PFC) in spleen and intestine. Two weeks after the first intragastric administration mice were given one parenteral injection of SRBC. In these mice the immunological response was reduced to 60% in relation to the results obtained in mice which had not any previous digestive contact with the antigen. These results support the view that thymus does not play a role in the induction of intragastrically induced immunosuppression.

[Relationship between orally induced immune tolerance and local immune response (author's transl)]. / Relation entre tolérance immunitaire induite par voie digestive et réponse immune locale.

BALB/c mice were immunized by intragastric immunization with sheep red blood cells repeated daily for 4 days. This immunization resulted in the appearance of circulating antibodies which were predominantly of the IgA class. When serum from intragastrically immunized mice was administered intraperitoneally to recipient animals 8 h before parenteral immunization with sheep red blood cells, the subsequent immune response was depressed proportionally to the dose of serum injected. When intragastrically immunized mice were challenged intraperitoneally with sheep red blood cells, the level of the IgM response to the parenteral stimulation was in inverse ratio to the IgA response induced by the oral route. These results suggest that orally induced IgA production is related to orally induced immune tolerance and that systemic hyporesponsiveness is achieved while gut plasma cells are producing specific IgA.