Rheumatoid factor (RF) IgM autoantibodies recognize the Fc portion of IgG and are commonly associated with autoimmune arthritis and immune complexmediated inflammation. RF IgM is frequently detected during early disease stages. Signosis has developed a mouse Anti-RF IgM ELISA kit to measure RF IgM levels in mouse serum, supporting studies of inflammatory arthritis, autoimmune mechanisms, and treatment response.