title: Analysis of the multiple interactions between IL-12 and the high affinity IL-12 receptor complex.
abstract: IL-12 is a heterodimeric cytokine, composed of a p40 and a p35 subunit, that exerts its biological effects by binding to specific cell surface receptors. Two IL-12R proteins, designated human IL-12 (huIL-12) receptor beta1 (huIL-12Rbeta1) and huIL-12Rbeta2, have been previously identified. These IL-12R individually bind huIL-12 with low affinity and in combination bind huIL-12 with high affinity and confer IL-12 responsiveness. In this study the interactions of hulL-12 with these two identified human IL-12R protein subunits are examined. The heterodimer-specific anti-huIL-12 mAb 20C2, which neutralizes huIL-12 bioactivity but does not block 125I-huIL-12 binding to huIL-12Rbeta1, blocked binding of huIL-12 to huIL-12Rbeta2. In contrast, anti-huIL-12Rbeta1 mAb 2B10 and mouse IL-12 p40 subunit homodimer (mo(p40)2) blocked 125I-huIL-12 binding to huIL-12Rbeta1, but not to huIL-12Rbeta2. Therefore, two classes of IL-12 inhibitors can be identified that differ in their ability to block huIL-12 interaction with either huIL-12Rbeta1 or huIL-12Rbeta2. Both mo(p40)2 and 20C2 blocked high affinity binding to huIL-12Rbeta1/beta2-cotransfected COS-7 cells, although, as previously reported, mo(p40)2 does not block high affinity binding to IL-12R on PHA-activated human lymphoblasts. Furthermore, these two classes of IL-12 inhibitors synergistically decreased hulL-12-stimulated proliferation and IFN-gamma production. Therefore, IL-12, in binding to the high affinity IL-12R, interacts with IL-12Rbeta1 primarily via regions on the IL-12 p40 subunit and with IL-12Rbeta2 via 20C2-reactive, heterodimer-specific regions of IL-12 to which the p35 and p40 subunits both contribute.
authors.affiliation: Department of Inflammation/Autoimmune Diseases, Hoffmann-La Roche Inc., Nutley, NJ 07110, USA.
authors.forename: D H
authors.initials: DH
authors.lastname: Presky
authors.forename: L J
authors.initials: LJ
authors.lastname: Minetti
authors.forename: S
authors.initials: S
authors.lastname: Gillessen
authors.forename: V L
authors.initials: VL
authors.lastname: Wilkinson
authors.forename: C Y
authors.initials: CY
authors.lastname: Wu
authors.forename: U
authors.initials: U
authors.lastname: Gubler
authors.forename: R
authors.initials: R
authors.lastname: Chizzonite
authors.forename: M K
authors.initials: MK
authors.lastname: Gately
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D001667:Binding, Competitive / Q000276:immunology; D019556:COS Cells; D019281:Dimerization; D004357:Drug Synergism; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology; D007371:Interferon-gamma / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D018664:Interleukin-12 / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism*; D007457:Iodine Radioisotopes / Q000378:metabolism; D007700:Kinetics; D008213:Lymphocyte Activation / Q000276:immunology; D011485:Protein Binding / Q000276:immunology; D018123:Receptors, Interleukin / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D053707:Receptors, Interleukin-12; D014162:Transfection
chemical_list: D000911:Antibodies, Monoclonal; C508438:IL12RB1 protein, human; C508439:IL12RB2 protein, human; C508440:Il12rb1 protein, mouse; C508443:Il12rb2 protein, mouse; D007166:Immunosuppressive Agents; D007457:Iodine Radioisotopes; D018123:Receptors, Interleukin; D053707:Receptors, Interleukin-12; D018664:Interleukin-12; D007371:Interferon-gamma