Pulmonary Activation Regulated Chemokine (PARC), also known as CCL18, is a small secreted protein belonging to the C-C chemokine family. It is primarily expressed by activated macrophages and dendritic cells in the lung. PARC mediates leukocyte recruitment during inflammation, particularly in allergic asthma and pulmonary fibrosis. Structurally, it contains conserved cysteine residues critical for receptor binding.PARC binds to CCR7, a G-protein-coupled receptor expressed on T cells and dendritic cells, promoting their migration to inflamed tissues and lymphoid organs, thereby regulating adaptive immune responses.Thus a functional ELISA assay was conducted to detect the interaction of recombinant human PARC and recombinant human CCR7. Briefly, PARC was diluted serially in PBS with 0.01% BSA (pH 7.4). Duplicate samples of 100 μl were then transferred to CCR7-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST and incubated for 1h with anti-PARC 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 450/630nm immediately. The binding activity of recombinant human PARC and recombinant human CCR7 was shown in Figure 1, the EC50?for this effect is 0.056ug/mL.