The interleukin-1 receptor antagonist (IL-1RA) is a member of the interleukin 1 cytokine family. IL1Ra is secreted by various types of cells including immune cells, epithelial cells, and adipocytes, and is a natural inhibitor of the pro-inflammatory effect of IL1β. IL-1RN is an agent that binds to the cell surface?interleukin-1 receptor?(IL-1R), which would prevent IL-1 from intracellular signal transduction. Thus, a binding ELISA assay was conducted to detect the interaction of recombinant rat IL-1RN and recombinant rat IL-1R1. Briefly, IL-1RA were diluted serially in PBS, with 0.01% BSA (pH 7.4). Duplicate samples of 100μl were then transferred to IL-1R1-coated microtiter wells and incubated for 2h at 37℃. Wells were washed with PBST and incubated for 1h with anti-IL-1RN pAb, then aspirated and washed 3 times. After incubation with HRP labelled secondary antibody, wells were aspirated and washed 3 times. With the addition of substrate solution, wells were incubated 15-25 minutes at 37℃. Finally, add 50μl stop solution to the wells and read at 450nm immediately. The binding activity of IL-1RA and IL-1R1 was shown in Figure 1, and this effect was in a dose dependent manner.