The antibody reacts specificly with human Interleukin (IL-1)RII. The IL-1 system includes two agonists (IL-1alpha and IL-1beta), converting enzymes, antagonists, two receptors (IL-1RI and IL-1RII) and the IL-1 receptor accessory protein. The IL-1RII is part of the antagonistic IL-1 mechanism. It is also known as decoy receptor and is a non signalling molecule which functions by capturing IL-1 and preventing it from interacting with the signalling IL-1RI. The decoy IL-1RII can after binding to IL-1 also recruit the IL-1 receptor accessory protein and thus inhibit by coreceptor competition. Further a soluble form of IL-1RII exists which is shed, a process in which matrix metalloproteases have been found to play a role, by various cells including monocytes, polymorphonuclear cells, B cells and fibroblasts.