Rheumatoid factor
Autoantibody found in rheumatoid arthritis / From Wikipedia, the free encyclopedia
Not to be confused with Rhesus factor.
Rheumatoid factor (RF) is the autoantibody that was first found in rheumatoid arthritis. It is defined as an antibody against the Fc portion of IgG and different RFs can recognize different parts of the IgG-Fc.[1] RF and IgG join to form immune complexes that contribute to the disease process such as chronic inflammation and joint destruction at the synovium and cartilage.[2]
Rheumatoid factor can also be a cryoglobulin (antibody that precipitates on cooling of a blood sample); it can be either type 2 (monoclonal IgM to polyclonal IgG) or type 3 (polyclonal IgM to polyclonal IgG) cryoglobulin.
Although predominantly encountered as IgM, rheumatoid factor can be of any isotype of immunoglobulins; i.e., IgA, IgG, IgM,[3] IgE,[4] IgD.[5]