Rheumatoid factor (RF)

Rheumatoid factor (RF) is an **autoantibody** that targets the Fc portion of immunoglobulin G (IgG) antibodies[1][3][10]. Most commonly, RF is of the IgM isotype but can also be of IgA, IgG, IgE, or IgD classes[1][3]. It forms immune complexes with IgG, which can contribute to chronic inflammation and tissue damage, especially in joint synovium and cartilage, playing a central role in diseases such as rheumatoid arthritis[1][3]. RF serves mainly as a **serological biomarker** for rheumatoid arthritis diagnosis and prognosis but is not specific to RA; it is present in various other autoimmune diseases (e.g., Sjögren syndrome, lupus), chronic infections, and even some healthy individuals[1][3][7][9]. High RF levels, particularly in RA, are associated with a worse prognosis and greater likelihood of extra-articular and severe systemic manifestations[3]. RF does not represent a therapeutic target (such as receptor, enzyme, or transporter); rather, it is a pathogenic and diagnostic autoantibody[2][6]. No drugs directly target RF, though it is used to monitor and guide therapy for RA and related conditions. Notes: - RF is a circulating autoantibody, not a receptor, enzyme, transporter, or cellular target as generally defined in therapeutic molecular targeting. - It is best considered a **biomarker** or pathogenic factor in autoimmunity, not a druggable target. - If a biological target is required (for drugs or precise molecular therapies), anti-citrullinated protein antibodies (ACPA) or specific B cell subtypes may be more appropriate choices. For structured data extraction, most fields related to drug interaction, therapeutic targeting, or direct molecular modulation are not directly applicable to rheumatoid factor.

Other names

RFrheumatoid arthritis factorRHF