The soluble form of IL-1 receptor accessory protein enhances the ability of soluble type II IL-1 receptor to inhibit IL-1 action

Immunity. 2003 Jan;18(1):87-96. doi: 10.1016/s1074-7613(02)00514-9.


Regulation of the activity of the proinflammatory cytokine IL-1 is complex, involving transcriptional and translational control, precursor processing, a receptor antagonist (IL-1ra), and a decoy receptor. Here we report that the soluble form of the IL-1 receptor accessory protein (AcP) increases the affinity of binding of human IL-1alpha and IL-1beta to the soluble human type II IL-1 receptor by approximately 100-fold, while leaving unaltered the low binding affinity of IL-1ra. Soluble AcP is present in normal human serum at an average concentration greater than 300 ng/ml. These findings suggest that the soluble form of IL-1R AcP contributes to the antagonism of IL-1 action by the type II decoy receptor, adding another layer of complexity to the regulation of IL-1 action.

MeSH terms

  • Alternative Splicing
  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Cell Line
  • Humans
  • Inflammation / immunology
  • Inflammation Mediators / metabolism
  • Interleukin-1 / metabolism*
  • Interleukin-1 Receptor Accessory Protein
  • Kinetics
  • Macaca mulatta
  • Molecular Sequence Data
  • Proteins / genetics
  • Proteins / metabolism*
  • Receptors, Interleukin-1 / metabolism*
  • Receptors, Interleukin-1 Type II
  • Recombinant Proteins / metabolism
  • Solubility


  • IL1RAP protein, human
  • Inflammation Mediators
  • Interleukin-1
  • Interleukin-1 Receptor Accessory Protein
  • Proteins
  • Receptors, Interleukin-1
  • Receptors, Interleukin-1 Type II
  • Recombinant Proteins

Associated data

  • GENBANK/AY182232
  • GENBANK/AY182233
  • GENBANK/AY182234