title: Biliary transport of IgA: role of secretory component.
abstract: Biliary transport of rat immunoglobulin was studied by perfusion of isolated rat liver with blood containing radiolabeled immunoglobulin. Transport to bile was selective for polymeric IgA. Between 15 and 27% of polymeric IgA was transported from blood to bile during a 210-min perfusion period, and approximately 60% of the IgA transported to bile bore secretory component. Small quantities of IgM (0.12%) were transported; transport of IgG2 alpha, IgE, or monomeric IgA was not detected. Purification of radiolabeled polymeric IgA by affinity chromatography on human secretory component-Sepharose yielded a fraction that was transported more efficiently (i.e., up to 40% transported). In contrast, secretory IgA (colostral or biliary) was transported 1/25th to 1/12th as well as polymeric IgA myeloma protein. Complexes of 125I-labeled secretory component and polymeric IgA formed in vitro were transported poorly (0.1%) compared to polymeric IgA (26%). It was concluded that biliary transport of polymeric IgA requires combination of it with secretory component in the liver. In support of this hypothesis, rabbit IgG anti-rat secretory component antibodies were also transported to bile but normal rabbit IgG was not.
mesh_terms: D000818:Animals; D001646:Bile / Q000276:immunology*; D001692:Biological Transport; D007070:Immunoglobulin A / Q000378:metabolism*; D007073:Immunoglobulin E / Q000378:metabolism; D007074:Immunoglobulin G / Q000378:metabolism; D066298:In Vitro Techniques; D007700:Kinetics; D008099:Liver / Q000276:immunology; D051381:Rats
chemical_list: D007070:Immunoglobulin A; D007074:Immunoglobulin G; D007073:Immunoglobulin E