The B122 monoclonal antibody reacts with precursor and mature secreted forms of mouse and rat IL-1β a 17 kDa pro-inflammatory cytokine produced primarily by monocytes. IL-1β is an important mediator of the inflammatory response, and is involved in a variety of cellular activities, including cell proliferation, differentiation, apoptosis, and T and B lymphocyte activation. IL-1 is made up of IL-1α and IL-1β which are the products of distinct genes, but which are recognized by two distinct IL-1 receptors. The IL-1 receptor type I, an 80 kDa transmembrane protein with demonstrated IL-1 signaling function and the IL-1 receptor type II, a 68 kDa membrane protein with a relatively short cytoplasmic tail. The type II receptor acts as a decoy target for IL-1, inhibiting IL-1 activities by preventing the binding of IL-1 to the type I receptor. The B122 antibody has been reported to neutralize the bioactivity of natural or recombinant IL-1β.