The monoclonal antibody M2139 reacts with the J1 epitope (triple helical position 551-564) of collagen type II. Collagen is a structural protein in bone, cartillage and connective tissue. Collagen type II (CII) is the major collagen of the nucleus pulposa (a component of spine), cartilage and vitreous (a component of the eye). The most commonly used animal model for rheumatoid arthritis (RA) is the collagen-induced arthritis (CIA). Transfer of collagen type II specific monoclonal antibodies induces an acute form of arthritis (collagen type II antibody induced arthritis, CAIA). The monocolonal antibody M2139 has been shown to induce CAIA in naïve mice after injection of lipopolysacharide (LPS). However, in combination with the monoclonal antibody CIIC1, binding to the C1 epitope of CII, the pair of monoclonal antibodies induce arthritis in different strains of mice without any other stimulants. The presence of secondary stimulus, LPS, increases the disease incidence and severity.