Development of an interleukin (IL)-33 sandwich ELISA kit specific for mature IL-33

Interleukin (IL)-33 is an inflammatory cytokine and belongs to the IL-1 family of cytokines. There are eleven members of the IL-1 family of cytokines and all have important roles in host defense against infections. Their levels are increased during infection and in various auto-inflammatory diseases. IL-33 is also associated with autoimmune diseases such as asthma, atopic dermatitis, rheumatoid arthritis, and atherosclerosis. IL-33 receptors consist of IL-1R4 and IL-1R3 to induce both Th1 and Th2 type immune response. Here we present the development of monoclonal antibodies (mAbs) against human mature IL-33. Recombinant human mature IL-33 protein was expressed in E. coli and purified by multi-step affinity chromatography. The human IL-33 activity was examined in HMC-1 and Raw 264.7 cells. Mice were immunized with the biologically active mature IL-33 to generate mAb against IL-33. The anti-IL-33 mAb (clone/4) was used as a capture antibody for a sandwich enzyme-linked immunosorbent assay (ELISA). This assay detects mature IL-33 with a high sensitivity (80 pg/mL) but does not recognize the biologically inactive precursor IL-33. This article describes the methods for a newly developed IL-33 ELISA kit that is specific for mature IL-33 and may be used to analyze bioactive mature IL-33 in various immunological diseases.