CAMP encodes Cathelicidin Antimicrobial Peptide, a key component of the innate immune system. Expressed in epithelial cells and immune cells, it exhibits broad-spectrum antimicrobial activity against bacteria, fungi, and viruses. Beyond pathogen elimination, it regulates inflammation and promotes wound healing, playing vital roles in host defense. CAMP binds with CTSG to enhance antimicrobial efficacy and modulate immune response synergistically.Thus a functional ELISA assay was conducted to detect the interaction of recombinant human CAMP and recombinant rat CTSG. Briefly, CAMP was diluted serially in PBS with 0.01% BSA (pH 7.4). Duplicate samples of 100 μl were then transferred to CTSG-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST and incubated for 1h with anti-CAMP 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 CAMP and recombinant rat CTSG was shown in Figure 1, the EC50?for this effect is 0.0076μg/mL.