For the quantitative determination of Human IL-33 levels in serum or other biological samples.*Buffers, Substrates and Plates are not included.Interleukin-1 (IL-1) family members, such as IL-19 and IL-18, play important roles in host defense, immune regulation, neuronal injury and inflammation (1, 2). Recently, a new member of this family, IL-33, has been reported. It mediates its biological effects via IL-1 receptor ST2 and activates NF-kB and MAPK pathways (3). IL-33 is synthesized in response to cytokines such as IL-1, and plays an important role in TH2-associated immunology. IL-33 expression drives production of TH2-associated cytokines from in vitro polarized TH2 cells and induces the expression of IL-4, IL-5, and IL-13 in vivo. Overexpression of IL-33 in mice leads to severe pathological changes in mucosal organs. IL-33 was previously identified as NF-HEV, a nuclear factor preferentially expressed in high endothelial venules HEV) (4). Recent studies revealed that IL-33 is a heterochromatin-associated nuclear factor and endothelial cells constitute a major source of IL-33 mRNA in chronically inflamed tissues from patients with rheumatoid arthritis and Crohn's disease(5). These data indicate that IL-33 is a dual function protein that may function as both a proinflammatory cytokine and an intracellular nuclear factor with transcriptional regulatory properties. The human IL-33 is expressed with a prodomain (aa 1-111) that is cleaved by caspase-1 to produce a 18kD protein (112-270) (6).Kit Contents: I8443-92Z1: Coating Antibody 1x80ulContains affinity-purified Chicken anti-human IL-33 at 1mg/ml.I8443-92Z2: Calibrator 1x4ul Contains Recombinant human IL-33 Antigen at 1mg/ml.Working Range: 500–0.7ng/mlI8443-92Z3: HRP Detection Antibody 1x12ulContains affinity-purified Chicken anti-human IL-33–HRP Conjugate at 0.6mg/ml.Buffers, Substrates and Plates are not included.Storage and Stability: For long-term storage, aliquot and store at -20°C. Aliquots are stable for at least 6 months at -20°C. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap. Further dilutions can be made in assay buffer.