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.