IL-1 refers to two proteins, IL-1α and IL-1β which are the products of distinct genes, but which are recognized by the same cell surface receptors. IL-1α is a potent immuno-modulator which mediates a wide range of immune and inflammatory responses. The ALF-161 antibody reacts with precursor, secreted and membrane-associated forms of mouse IL-1α. The ALF-161 antibody can neutralize the bioactivity of natural or recombinant IL-1α.