autoantibody

Autoantibody refers to an antibody that targets the body's own tissues or components, produced when immune tolerance to self-antigens is impaired. Autoantibodies can be of various isotypes, most commonly IgG or IgM, and may be present in health or disease. They can arise from genetic susceptibility, environmental triggers, or infections that alter self-antigens or immune regulation.

The presence of autoantibodies does not always indicate autoimmune disease. They can serve as markers identifying a particular condition, aid in diagnosis, and help monitor disease activity. Some autoantibodies are directly pathogenic, contributing to tissue injury through mechanisms such as immune complex formation and complement activation, interference with receptor signaling, antibody-dependent cellular cytotoxicity, or triggering inflammatory pathways. Others may be incidental or reflect a broader dysregulation of B cell tolerance.

Common examples include antinuclear antibodies (ANA), which are detected in many autoimmune diseases and used as a screening tool; anti-dsDNA and anti-Sm antibodies, which are relatively specific for systemic lupus erythematosus; antiphospholipid antibodies associated with thrombotic risk; and rheumatoid factor or anti-CCP antibodies in rheumatoid arthritis. Organ-specific autoantibodies include anti-TPO and anti-thyroglobulin in autoimmune thyroid disease, acetylcholine receptor antibodies in myasthenia gravis, and desmoglein antibodies in pemphigus.

Detection methods include indirect immunofluorescence for screening, enzyme-linked immunosorbent assays (ELISAs), immunoblot techniques, and multiplex panels. Interpreting autoantibody results requires clinical context, as false positives can occur and positivity may precede overt disease.