Characterization and identification of interleukin-1 receptors on bovine fibroblasts

Abstract

Interleukin-1 (IL-1), a pro-inflammatory cytokine, initiates its many biological effects by first binding to cell-surface receptors. Prior to this study, there were no published reports addressing the nature of the bovine IL-1 receptor. In this study, we characterized and identified cell-surface IL-1 receptors on bovine fibroblasts. Direct binding studies using [ 125I]-labeled bovine IL-1β demonstrated that bovine fibroblasts had approximately 130 high affinity and 2,500 low affinity binding sites (Kd = 4.9 × 10 −11 M and 3.7 × 10 −9M, respectively). Competitive binding studies using unlabeled recombinant bovine IL-1β, IL-2, IFN-α, and bovine insulin demonstrated that only unlabeled bovine IL-1β competitively blocked fibroblast binding of [ 125I]-labeled bovine IL-1β. Affinity cross-linking of [ 125I]-labeled IL-1β to fibroblasts demonstrated that IL-1 receptors on bovine fibroblasts have an apparent M r of 71.5 kD. This report provides the first characterization and identification of IL-1 receptors on bovine fibroblasts.