Relevance of biliary IgA antibodies in rat intestinal immunity.

Two intraperitoneal administrations of foreign red cells in Freund's complete adjuvant, or two intragastric intubations of erythrocytes, given to rats at 15 days interval, both elicit the appearance of specific antibodies in bile and serum. When bile was compared to serum, the selective predominance of IgA antibodies in this secretion was observed for both the intraperitoneally and intragastrically immunized groups, being more pronounced for the orally immunized group when related to IgG or IgM antibodies. The IgA content of upper intestinal washings was roughly ten-fold smaller in rats with bile duct cannulation than in sham-operated controls. Altogether, the data demonstrate that bile IgA may significantly contribute to the secretory IgA system of the gut.