Eosinophil Peroxidase (EPX) is a key enzyme exclusively expressed in eosinophils, a type of white blood cell. It plays a central role in the immune system’s defense against parasitic infections and participates in regulating inflammatory responses. EPX catalyzes the production of hypohalous acids, which exhibit strong antimicrobial activity to eliminate pathogens. Abnormal EPX expression or function is linked to allergic diseases like asthma and chronic eosinophilic disorders. EPX and Ribonuclease A3 (RNASE3) interact in eosinophils; this binding modulates their respective antimicrobial and pro-inflammatory activities to coordinate immune responses.To detect the activity of recombinant EPX , a functional ELISA assay was performed to evaluate the interaction between recombinant human EPX and recombinant human RNASE3.Briefly, EPX was diluted serially in PBS with 0.01% BSA (pH 7.4). Duplicate samples of 100 μl were then transferred to RNASE3-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST and incubated for 1h with anti-EPX 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 EPX and human RNASE3
was shown in Figure 1, the EC50 for this effect is 0.042µg/mL.