RF elevation occurs due to interaction between which immunoglobulin classes?

RF elevation occurs due to interaction between which immunoglobulin classes?

• A. IgMs reacting to IgG in synovial fluid
• B. IgGs reacting to IgMs
• C. IgEs reacting to IgG
• D. IgAs reacting to IgM

Answer: (A)

Rheumatoid factor is an autoantibody that targets the Fc portion of IgG, and the classic form is IgM. These IgM anti-IgG antibodies bind to IgG, creating immune complexes that can deposit in the synovium and activate complement, fueling inflammation and the joint damage seen in rheumatoid arthritis. So the elevation arises from IgMs reacting with IgG in the joint environment, including synovial fluid. The other interactions—IgG against IgM, IgE against IgG, or IgA against IgM—do not describe the typical RF mechanism and are not the basis for RF elevation in RA.

Rheumatoid factor is an autoantibody that targets the Fc portion of IgG, and the classic form is IgM. These IgM anti-IgG antibodies bind to IgG, creating immune complexes that can deposit in the synovium and activate complement, fueling inflammation and the joint damage seen in rheumatoid arthritis. So the elevation arises from IgMs reacting with IgG in the joint environment, including synovial fluid. The other interactions—IgG against IgM, IgE against IgG, or IgA against IgM—do not describe the typical RF mechanism and are not the basis for RF elevation in RA.