Antibodies to domains II and III of the IL-1 receptor accessory protein inhibit IL-1 beta activity but not binding: regulation of IL-1 responses is via type I receptor, not the accessory protein.
The IL-1R accessory protein (IL-1RAcP) plays a role in IL-1R signaling by forming a complex with IL-1RI bound to the IL-1 ligand. We identified four hydrophilic peptide regions of the extracellular IL-1RAcP that may be available for complex formation (peptide 1, 71-83 domain I; peptide 2, 204-211 domain II; peptide 3, 282-292 domain III; and peptide 4, 304-314 domain III). These peptides were synthesized, coupled to keyhole limpet hemocyanin, and used to produce rabbit antisera. Each affinity-purified antiserum showed specificity for the respective peptide without cross-reactivity. Anti-peptide 2, 3, and 4 recognized surface expression of IL-1RAcP on the Th2 D10S cells by FACS and inhibited IL-1-driven proliferation. Anti-peptide 4 recognized intact IL-1RAcP and soluble IL-1RAcP. Anti-IL-1RAcP-peptide 4, which targets the terminal segment of domain III, inhibited 80% of IL-1 beta-driven proliferation of D10S cells. However, these IL-1RAcP Abs had no effect on the activity of human or mouse IL-1 alpha. Whereas IL-1 beta down-regulated IL-1RI surface expression (p < 0.05), there was no change in the surface expression of IL-1RAcP. Moreover, murine IL-10 increased surface expression of IL-1RI, but did not affect expression of IL-1RAcP or the proliferation of D10S cells. Steady state levels of mRNA for IL-1RAcP and IL-1RI in D10S cells showed a similar pattern to that of surface expression of the respective receptors. We conclude that 1) blocking IL-1RAcP inhibits IL-1 signaling in D10S cells, 2) domains-II and III may be involved in complex formation with IL-1RI, 3) IL-1RAcP is not regulated as is IL-1RI in the same cells, and 4) IL-1 responsiveness is dependent on the expression of IL-1RI, not IL-1RAcP.
Yoon
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Division of Infectious Diseases, University of Colorado Health Sciences Center, Denver 80262, USA.
Dinarello
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D000818:Animals; D000906:Antibodies / Q000378:metabolism / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects / Q000276:immunology; D002460:Cell Line; D006801:Humans; D007106:Immune Sera / Q000096:biosynthesis; D007166:Immunosuppressive Agents / Q000494:pharmacology; D007375:Interleukin-1 / Q000037:antagonists & inhibitors* / Q000378:metabolism / Q000494:pharmacology; D053577:Interleukin-1 Receptor Accessory Protein; D016753:Interleukin-10 / Q000494:pharmacology; D008213:Lymphocyte Activation / Q000187:drug effects / Q000276:immunology; D051379:Mice; D009842:Oligopeptides / Q000138:chemical synthesis / Q000276:immunology / Q000494:pharmacology; D011485:Protein Binding / Q000276:immunology; D014176:Protein Biosynthesis; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000276:immunology*; D017472:Receptors, Interleukin-1 / Q000276:immunology* / Q000378:metabolism* / Q000502:physiology
D000906:Antibodies; C507765:IL1RAP protein, human; C507767:Il1rap protein, mouse; D007106:Immune Sera; D007166:Immunosuppressive Agents; D007375:Interleukin-1; D053577:Interleukin-1 Receptor Accessory Protein; D009842:Oligopeptides; D011506:Proteins; D017472:Receptors, Interleukin-1; D016753:Interleukin-10