How are rheumatoid factors defined?

Rheumatoid factors are defined as autoantibodies that specifically target the Fc portion of IgG. They are commonly found in individuals with rheumatoid arthritis and other autoimmune disorders. The presence of these autoantibodies is important because they can form immune complexes, which may contribute to inflammation and tissue damage in joints.

Understanding that rheumatoid factors bind to the Fc region of IgG helps clarify their role in the pathophysiology of autoimmune diseases. This interaction is significant in the formation of these immune complexes, which can activate complement pathways and recruit immune cells, exacerbating inflammatory responses in affected tissues.

The other options do not accurately describe rheumatoid factors. For example, option A refers to autoantibodies binding to IgA, which is not the primary characteristic of rheumatoid factors. Option C incorrectly states that they target the Fab region, which is not relevant to their known action. Option D, mentioning inhibition of B cell activity, misrepresents the function of rheumatoid factors, as their involvement is more about promoting inflammation than inhibiting B cell functions.