Recombinant Human IL-1 RI Fc Chimera Protein, CF

The type I IL-1 receptor (IL-1 RI, designated IL-1 R1 and CD121a) is one of at least nine members of the IL-1 R family within the Toll/IL-1 R (TIR) superfamily (1 - 3). IL-1 RI is an 80 kDa type I transmembrane (TM) protein that binds the pleiotropic cytokines IL-1 alpha and IL-1 beta, plus the IL-1 receptor antagonist (IL-1 Ra). Signal transduction requires complex formation with the IL-1 R accessory protein (IL-1 R AcP/IL-1 R3), another type I TM protein (1, 2). This complex recruits the adaptor protein MyD88, to initiate signaling in the NF kappaB pathway (4, 5). Human IL-1 RI cDNA encodes a 569 amino acid (aa) protein that contains a 17 aa signal sequence, a 319 aa extracellular domain (ECD) with three C2-type Ig-like domains, a 20 aa TM domain and a 213 aa cytoplasmic region with a TIR domain. Within the ECD domain, human IL-1 RI shares 63% and 64% aa identity with mouse and rat IL-1 RI, respectively.  The role of IL-1 in inflammation is under several levels of control, including expression and activation of IL-1 alpha and IL-1 beta, expression of IL-1 RI and its accessory and adaptor proteins, and inhibitory IL-1 R isoforms and decoys (1 - 5). IL-1 RI is expressed predominantly by T cells, fibroblasts, and endothelial cells and mediates acute phase inflammatory responses including fever (1, 2, 5, 6).