Biliary transport of serum IgA in sheep

The existence of a hepato-biliary pump for IgA has been studied in sheep by measuring appearance of radioactivity in bile after simultaneous i.v. injection of IgG2 and homologous dimeric IgA each labelled with either 125I or 131I. These experiments confirm that in sheep, as in rodents, IgA is the predominant immunoglobulin in bile and is selectively transported into bile from serum relative to IgG2. In addition, there is evidence for local production of IgA in bile presumably by plasma cells within the liver and biliary tree.