The elimination of circulating complexes containing polymeric IgA by excretion in the bile.

Radiolabelled human dimeric IgA injected intravenously into rats behaved like oligomeric rat IgA in that 40% of the injected dose was recovered in the bile within 6 h. Monomeric IgA was not transported into bile. In addition, dimeric IgA was able to carry with it macromolecular material in the form of a complex that also included rat SC. This was demonstrated in rats which had received an intravenous injection of specifically purified radiolabelled rabbit antibody tao the idiotype of a human IgA myeloma: when a later injection of unlabelled IgA dimer with the corresponding idiotype was given up to 18% of the rabbit antibody when the monomeric form of the same IgA was injected. This mechanism for clearing complexes containing polymeric IgA is mediated by hepatocytes and is distinct from the phagocyte-mediated mechanisms which clear conventional complexes.