title: Involvement of alpha-2-macroglobulin receptor in clearance of interleukin 8-alpha-2-macroglobulin complexes by human alveolar macrophages.
abstract: The purpose of this study was to determine if interleukin 8 (IL-8) in complex with alpha2-macroglobulin (alpha-2-M) can be taken up by human alveolar macrophages. First, we demonstrated that human alveolar macrophages have receptors for alpha-2-M but not IL-8. The binding of(125)I-labeled alpha-2-M to the cells was specific and saturable, whereas(125)I-labeled recombinant human IL-8 (rhIL-8) did not bind to macrophages. However,(125)I-rhIL-8-alpha-2-M complexes bound to macrophages, and unlabeled alpha-2-M competed for the binding. We then cultured the cells in the presence of(125)I-rhIL-8-alpha-2-M complexes,(125)I-rhIL-8 alone or buffer for 24 h. Macrophages were lysed, and the released radioactivity measured. IL-8 concentrations in supernatants and cells were also measured using an IL-8 ELISA. When the macrophages were incubated with(125)I-rhIL-8-alpha-2-M complexes there was a significant amount of IL-8 associated with the cells. However, this was not the case when the cells were incubated with(125)I- rhIL-8 alone suggesting that only these complexes were taken-up by human alveolar macrophages. Furthermore, the clearance of complexes was specifically inhibited by a monoclonal antibody against the 515-kDa subunit of the alpha-2-M receptor (alpha-2-MR) but not by an isotopic mouse IgG1. The study shows an important clearance mechanism for IL-8 in the lung.
authors.affiliation: Department of Biochemistry, University of Texas Health Center at Tyler, 75708, USA. ANNA@uthct.edu
authors.forename: A
authors.initials: A
authors.lastname: Kurdowska
authors.forename: S M
authors.initials: SM
authors.lastname: Alden
authors.forename: J M
authors.initials: JM
authors.lastname: Noble
authors.forename: M D
authors.initials: MD
authors.lastname: Stevens
authors.forename: F K
authors.initials: FK
authors.lastname: Carr
mesh_terms: D000818:Animals; D006801:Humans; D016209:Interleukin-8 / Q000008:administration & dosage / Q000378:metabolism* / Q000493:pharmacokinetics; D007457:Iodine Radioisotopes; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D016676:Macrophages, Alveolar / Q000378:metabolism*; D051379:Mice; D011971:Receptors, Immunologic / Q000378:metabolism*; D000511:alpha-Macroglobulins / Q000008:administration & dosage / Q000378:metabolism* / Q000493:pharmacokinetics
chemical_list: D016209:Interleukin-8; D007457:Iodine Radioisotopes; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D011971:Receptors, Immunologic; D000511:alpha-Macroglobulins