Interleukin 13 (IL13) is cytokine secreted by many cell types, but especially T helper type 2 (Th2) cells. IL13 has effects on immune cells that are similar to those of the closely related cytokine IL4. Although IL13 is associated primarily with the induction of airway disease, it also has anti-inflammatory properties. IL13 induces a class of protein-degrading enzymes, known as matrix metalloproteinases (MMPs), in the airways. Furthermore, IL-13 can induce immunoglobulin E (IgE) secretion from activated human B cells. Besides, Interleukin 13 Receptor Alpha 1 (IL13Ra1) has been identified as an interactor of IL13, thus a functional binding ELISA assay was conducted to detect the interaction of recombinant human IL13 and recombinant mouse IL13Ra1. Briefly, biotin-linked IL13 were diluted serially in PBS, with 0.01% BSA (pH 7.4). Duplicate samples of 100 μl were then transferred to IL13Ra1-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST 3 times and incubation with Streptavidin-HRP for 30min, then wells were aspirated and washed 5 times. With the addition of substrate solution, wells were incubated 15-25 minutes at 37℃. Finally, add 50 µl stop solution to the wells and read at 450 nm immediately. The binding activity of IL13 and IL13Ra1 was shown in Figure 1, the EC50 for this effect is 0.018 ug/mL.