IgA antibodies in rat bile inhibit cholera toxin-induced secretion in ileal loops in situ.

The biological actions of IgA antibodies in bile are largely undefined. We therefore tested whether biliary IgA antibodies could specifically inhibit cholera enterotoxin (CT)-induced secretion in the rat ileum. Rats were immunized by CT given orally or by injection into Peyer's patches. Bile was collected by bile duct cannulation, and anti-CT antibodies in the bile were measured by ELISA. CT plus bile from either immunized or unimmunized rats, or CT plus anti-CT-containing bile which had been absorbed by a CT immunosorbent, were instilled into in situ ileal loops in unimmunized rats; CT alone, or buffer was instilled into other loops. The bile used from the immunized rats contained IgA, but neither IgG nor IgM, anti-CT antibodies. It was found that bile containing IgA anti-CT antibodies almost totally inhibited the secretory effect of CT, and this inhibition was abrogated by absorption of the IgA anti-CT antibodies. Thus, IgA antibodies to an enterotoxin, secreted into bile, are effective against the enterotoxin in the rat intestine in vivo.