Intracellular Staining by Flow Cytometry
|Detection of IL‑1 beta /IL‑1F2 in LPS-treated Peripheral Blood Mononuclear Cell Monocytes by Flow Cytometry. Peripheral blood mononuclear cell monocytes, resting (open histogram) or treated with LPS (filled histogram), were stained with Mouse Anti-Human IL‑1 beta /IL‑1F2 PerCP‑conjugated Monoclonal Antibody (Catalog # IC201C) or isotype control antibody (Catalog # IC002C). View our protocol for Staining Intracellular Molecules.|
IL-1 is a name that defines two 17 kDa pleiotropic cytokines, IL-1 alpha (IL-1F1) and IL-1 beta (IL-1F2), both of which are the products of distinct genes. IL-1 alpha and IL-1 beta are structurally related single-chain polypeptides that share approximately 21% amino acid (aa) identity in human. Although IL-1 ( alpha and beta ) references two distinct molecules, the term IL-1 is also generally applied to an eleven-member protein family that exhibits an Ala-xxx-Asp motif in its primary structure (1,3). IL-1 alpha and beta are not redundant. IL-1 alpha is constitutively expressed, contains an NLS, is active as a proform, and may present as a membrane-bound form due to myristoylation and glycosylation (4). Both proteins are produced by a wide variety of cells in response to inflammatory agents, infections, or microbial endotoxins. While IL-1 alpha and IL-1 beta are regulated independently, and they bind to the same cell surface receptor, the functional 80 kDa IL-1 RI binds directly to IL-1 alpha or IL-1 beta and then associates with IL-1 R accessory protein (IL-1 R3/IL-1 R AcP) to form a high-affinity receptor complex that is competent for signal transduction. IL-1 RII has high affinity for IL-1 beta but functions as a decoy receptor and negative regulator of IL-1 beta activity. IL-1ra, a third member of the IL-1 subfamily that also includes IL-33, functions as a competitive antagonist by preventing IL-1 alpha and IL-1 beta from interacting with IL-1 RI (2,3). The human IL-1 beta cDNA encodes a 269 aa precursor that contains a 116 aa propeptide that is cleaved intracellularly by the inflammasome-associated cysteine protease IL-1 beta -converting enzyme (Caspase-1/ICE) to generate an active 153 aa cytokine (3,5,6). The 17 kDa mature human IL-1 beta shares 96% aa sequence identity with rhesus and 67-78% aa sequence identity with canine, cotton rat, equine, feline, mouse, porcine, and rat IL-1 beta.