Thymic stromal lymphopoietin (TSLP) is a member of the IL-2 cytokine family and a distant paralog of IL-7. TSLP is a pleiotropic cytokine that acts on multiple cell lineages, including dendritic cells, T cells, B cells, neutrophils, mast cells, eosinophils and innate lymphoid cells, affecting their maturation, survival and recruitment. It is best known for its role in promoting type 2 immune responses such as in allergic diseases. Interleukin 13 (IL13) is a critical downstream element for TSLP-driven allergic inflammation. Thus a functional binding ELISA assay was conducted to detect the interaction of recombinant human TSLP and recombinant bovine IL13. Briefly, TSLP was diluted serially in PBS with 0.01% BSA (pH 7.4). Duplicate samples of 100 μl were then transferred to IL13-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST and incubated for 1h with anti-TSLP pAb, then aspirated and washed 3 times. After incubation with HRP labelled secondary antibody for 1h at 37℃, 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 450/630 nm immediately. The binding activity of recombinant human TSLP and recombinant bovine IL13 was shown in Figure 1, the EC50 for this effect is 0.11 ug/mL.