Macrophage Inflammatory Protein 3 Alpha (MIP3a) also known as Chemokine (C-C motif) ligand 20 (CCL20) or liver activation regulated chemokine (LARC) is a small cytokine belonging to the CC chemokine family. It is strongly chemotactic for lymphocytes and weakly attracts neutrophils. MIP3a is implicated in the formation and function of mucosal lymphoid tissues via chemoattraction of lymphocytes and dendritic cells towards the epithelial cells surrounding these tissues. It is expressed in several tissues such as peripheral blood lymphocytes, lymph nodes, liver, appendix, fetal lung. Expression of MIP3a can be induced by microbial factors such as lipopolysaccharide (LPS), and inflammatory cytokines such as tumor necrosis factor and interferon-γ, and down-regulated by IL-10. Besides, lnterleukin 1 Alpha (IL1a) has been identified as an interactor of MIP3a, thus a binding ELISA assay was conducted to detect the interaction of recombinant human MIP3a and recombinant human IL1a. Briefly, MIP3a were diluted serially in PBS, with 0.01% BSA (pH 7.4). Duplicate samples of 100 ul were then transferred to IL1a-coated microtiter wells and incubated for 2h at 37℃. Wells were washed with PBST and incubated for 1h with anti-MIP3a pAb, then aspirated and washed 3 times. After incubation with HRP labelled secondary antibody, 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 450nm immediately. The binding activity of MIP3a and IL1a was shown in Figure 1, and this effect was in a dose dependent manner, the EC50 for this effect is 0.676 ug/mL.