title: Binding, internalization and degradation of soluble aggregates of human secretory IgA by resident rat peritoneal macrophages.
abstract: In the present study the in vitro binding, internalization and degradation of IgA immune complexes (IC) by phagocytes was studied. As a model for IgA IC, heat-aggregated human secretory IgA (AsIgA) was prepared and resident rat peritoneal macrophages (PM phi) were used as a source of phagocytes. First, binding of 125I-AsIgA to rat PM phi was investigated. Binding of 125I-AsIgA to PM phi at 4 degrees was saturable and reached plateau values after 2 hr. At 37 degrees, degradation of membrane-bound 125I-AsIgA into trichloroacetic acid (TCA)-soluble fragments occurred. Parallel experiments with unlabelled AsIgA and 125I-labelled anti-human IgA revealed that degradation of AsIgA was preceded by internalization of AsIgA. The specificity of binding of 125I-AsIgA to PM phi was investigated using human IgG, human serum IgA, human myeloma IgA1, human sIgA and the glycoproteins asialofetuin and ovalbumin. The binding of 125I-AsIgA to rat PM phi was inhibited in the presence of sIgA and asialofetuin. In contrast IgG and ovalbumin had no effect. These results suggest that receptors with a specificity for galactose on the rat PM phi are involved in the binding of AsIgA.
authors.affiliation: Department of Nephrology, University Hospital Leiden, The Netherlands.
authors.forename: A
authors.initials: A
authors.lastname: Gorter
authors.forename: P S
authors.initials: PS
authors.lastname: Hiemstra
authors.forename: N
authors.initials: N
authors.lastname: Klar-Mohamad
authors.forename: L A
authors.initials: LA
authors.lastname: van Es
authors.forename: M R
authors.initials: MR
authors.lastname: Daha
mesh_terms: D000818:Animals; D000936:Antigen-Antibody Complex / Q000378:metabolism*; D001667:Binding, Competitive; D006358:Hot Temperature; D007071:Immunoglobulin A, Secretory / Q000276:immunology / Q000378:metabolism*; D007700:Kinetics; D008264:Macrophages / Q000502:physiology*; D010529:Peritoneal Cavity / Q000276:immunology; D010587:Phagocytosis; D011489:Protein Denaturation; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D000936:Antigen-Antibody Complex; D007071:Immunoglobulin A, Secretory