Integrin Alpha X (CD11c) is a member of the leukointegrin family, it is an approximately 150 kDa type I transmembrane glycoprotein that heterodimerizes with Integrin beta 2. One of the earliest described properties of CD11c is its ability to mediate phagocytosis of iC3b-opsonized particles. Accordingly, CD11c is known as complement receptor 4. CD11c has also been implicated in phagocytosis of latex beads and bacteria in the absence of complement. CD11c binds a diverse array of ligands such as cell adhesion molecules and Interleukin 13 (IL13). Thus a functional binding ELISA assay was conducted to detect the interaction of recombinant human CD11c and recombinant bovine IL13. Briefly, CD11c 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-CD11c 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 CD11c and recombinant bovine IL13 was shown in Figure 1, the EC50?for this effect is 0.28 ug/mL.