Immunoglobulin E (IgE) is a key antibody isotype primarily responsible for type I hypersensitivity and allergic responses. Identified in 1968, IgE is synthesized by plasma cells and binds with high affinity to FcεRI on mast cells and basophils. Upon allergen exposure, cross-linking of IgE-receptor complexes triggers degranulation and release of inflammatory mediators, leading to allergic symptoms such as rhinitis, asthma, urticaria, and anaphylaxis. Beyond allergy, IgE also participates in host defense against parasitic infections. It exists at low concentrations in serum but is highly concentrated on effector cell surfaces, making it a central target for diagnostic and therapeutic interventions in allergic diseases. PPARa negatively regulates IgE production and IgE receptor expression to suppress allergic inflammation. Briefly, PPARa was diluted serially in PBS with 0.01% BSA (pH 7.4). Duplicate samples of 100 μl were then transferred to IgE-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST and incubated for 1h with anti-PPARa 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. Measured by its binding ability in a functional ELISA. When Recombinant IgE is lmmobilized at 2 µg/mL(100 µLwell), the concentration of PPARa that produces 50% optimal bindingresponse is found to be approximately 0.058 µg/mL.