CellaQuant™ Human IL-33 (Interleukin 33) ELISA Kit (CQH020)

This ELISA kit uses the Sandwich-ELISA principle. The micro ELISA plate provided in this kit has been pre-coated with an antibody specific to Human IL-33. Samples (or Standards & Quality Control Material) are added to the micro ELISA plate wells and combined with the specific antibody. Then a biotinylated detection antibody specific for Human IL-33 and Avidin-Horseradish Peroxidase (HRP) conjugate are added successively to each micro plate well and incubated. Free components are washed away. The substrate solution is added to each well. Only those wells that contain Human IL-33, biotinylated detection antibody and Avidin-HRP conjugate will appear blue in color. The enzyme-substrate reaction is terminated by the addition of stop solution and the color turns yellow. The optical density (OD) is measured spectrophotometrically at a wavelength of 450±9 nm. The OD value is proportional to the concentration of Human IL-33. You can calculate the concentration of Human IL-33 in the samples by comparing the OD of the samples to the standard curve.

Interleukin-33 (IL-33) is a dual-function protein belonging to the IL-1 cytokine family, discovered independently as DVS27 and nuclear factor from high endothelial venules (NF-HEV). It is constitutively expressed as a 30 kDa pro-form, notably in vascular smooth muscle, endothelial cells, and airway epithelia. In its full-length form, IL-33 localizes to the nucleus via a nuclear localization sequence, where it binds chromatin and can act as a transcriptional regulator, potentially repressing NF-κB target genes in quiescent endothelium.Upon cellular stress or damage, full-length IL-33 is processed by inflammatory caspases (e.g., caspase-1) into a mature, bioactive cytokine. This mature form functions as a potent "alarmin," signaling through a receptor complex comprising ST2 (IL1RL1) and IL-1RAcP. This engagement activates canonical NF-κB and MAPK pathways.IL-33 is a central driver of type 2 immunity. It promotes Th2 cell differentiation and the secretion of cytokines like IL-5 and IL-13, activates mast cells, eosinophils, and basophils, and enhances alternative (M2) macrophage polarization. Consequently, it plays key roles in allergic inflammation, helminth responses, and tissue repair. Its rapid release from damaged cells positions IL-33 as a critical sentinel at the interface of innate and adaptive immunity.