An Antibody to a 17 Amino Acid Synthetic Peptide of the Type I Interleukin-1 Receptor Preferentially Blocks Interleukin-1β Binding

On the basis of their relative hydropathy and α-helical structure, we prepared antibodies to four synthetic peptides with amino acid sequences homologous to four hydrophilic, extracellular regions of the murine 80 kDa type I interleukin-1 receptor (IL-1RI). Antibodies to each of the four peptides recognized their specific immunogen. Human [125I]-IL-lα or -β was crosslinked to murine EL4 and D10S cells. Antiserum to peptide 150-166 precipitated the IL-1/IL-1R complex, whereas antibodies to peptide 66-84, 190-200, or 266-285 did not. Antibody to peptide 150-166 did not precipitate the type II IL-1R. Anti-IL-1RI150-166 blocked 71% of the binding of radiolabeled human IL-1β to EL4 cells and 50% of the binding to D10S cells. Using affinity-purified anti-IL-1RI150-166, we compared the ability of this antibody to inhibit the binding of murine or human IL-1α to that of murine or human IL-1β. At a concentration of 20 ng/ml, affinity-purified anti-IL-1RI150-166 blocked 50% binding of murine IL-1β. At 1 μg/ml, 90% b...