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 ass°Ciated 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 binding ELISA assay was conducted to detect the interaction of recombinant rat IL13 and recombinant rat IL13Ra1. Briefly, IL13 were diluted serially in PBS, with 0.01% BSA (pH 7.4). Duplicate samples of 100uL were then transferred to IL13Ra1-coated microtiter wells and incubated for 2h at 37°C. Wells were washed with PBST and incubated for 1h with anti-IL13 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°C. Finally, add 50µL stop solution to the wells and read at 450nm immediately. The binding activity of IL13 and IL13Ra1 was shown in Figure 1, and this effect was in a dose dependent manner.