Collagen-induced arthritis (CIA) is an experimental autoimmune disease that is widely used as a model of human rheumatoid arthritis (RA) in the study of the pathogenic mechanisms of this disease and for testing potential therapeutics. Circulating levels of anti-type II collagen antibody are strongly associated with the development of arthritis and can be used as a biomarker of CIA. Cayman’s Mouse Anti-Type II Collagen IgG Assay is an immunometric (i.e., sandwich) assay which can be used to measure anti-type II collagen antibody in plasma or serum without prior sample purification. This kit uses a bovine collagen-coated plate and an affinity-purified polyclonal antibody isolated from mice with CIA as a standard. This standard provides the most accurate measurement of anti-CII concentration in experimental plasma samples. One unit of standard in this assay is approximately equal to 1 ng of IgG protein. The standard curve spans the range of 15.6-1,000 U/ml, with an LLOQ of 15.6 U/ml.