Analysis of the multiple interactions between IL-12 and the high affinity IL-12 receptor complex

J Immunol. 1998 Mar 1;160(5):2174-9.


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.

MeSH terms

  • Animals
  • Antibodies, Monoclonal / pharmacology
  • Binding, Competitive / immunology
  • COS Cells
  • Dimerization
  • Drug Synergism
  • Humans
  • Immunosuppressive Agents / pharmacology
  • Interferon-gamma / antagonists & inhibitors
  • Interferon-gamma / biosynthesis
  • Interleukin-12 / antagonists & inhibitors
  • Interleukin-12 / immunology
  • Interleukin-12 / metabolism*
  • Iodine Radioisotopes / metabolism
  • Kinetics
  • Lymphocyte Activation / immunology
  • Protein Binding / immunology
  • Receptors, Interleukin / biosynthesis
  • Receptors, Interleukin / chemistry
  • Receptors, Interleukin / metabolism*
  • Receptors, Interleukin-12
  • Transfection


  • Antibodies, Monoclonal
  • IL12RB1 protein, human
  • IL12RB2 protein, human
  • Il12rb1 protein, mouse
  • Il12rb2 protein, mouse
  • Immunosuppressive Agents
  • Iodine Radioisotopes
  • Receptors, Interleukin
  • Receptors, Interleukin-12
  • Interleukin-12
  • Interferon-gamma