What is rheumatoid factor and how is it related to rheumatoid arthritis?

Rheumatoid factor is a high-molecular-weight autoantibody—specifically an antibody that reacts against IgG immunoglobulins—often found in the blood of individuals with rheumatoid arthritis.123

In the context of rheumatoid arthritis, an autoimmune disease characterized by chronic inflammation of the synovial membranes in the joints, rheumatoid factor plays a significant role in the disease process. It binds to IgG molecules to form immune complexes that are deposited within the synovial membrane. This deposition triggers a hypersensitivity reaction that activates the immune system, leading to the release of enzymes that erode and destroy cartilage and joint structures.23

Because these autoantibodies are present in many patients, a rheumatoid factor test is a standard diagnostic tool used alongside imaging and other blood tests. However, it is important to note that the disease can occur even in patients where no rheumatoid factor is detected, indicating that other immune mechanisms also contribute to the development of this condition.23