Selfantigens

Self-antigens are molecules or epitopes derived from the body's own tissues that can be recognized by the immune system. They include proteins, nucleic acids, lipids, and complex surface structures found on cells and in tissues. Normally, the immune system maintains tolerance to self-antigens through central tolerance in the thymus and bone marrow, peripheral tolerance, and regulatory T cells, preventing harmful immune responses against the body's own components.

Autoimmune disease can occur when tolerance is breached, allowing self-antigens to trigger immune reactions. This can involve autoantibodies produced by B cells and autoreactive T cells that damage tissues or alter function. Self-antigens implicated in disease include nuclear antigens such as double-stranded DNA, histones, Sm and RNP complexes (common in systemic lupus erythematosus); thyroid antigens such as thyroglobulin and thyroid peroxidase; organ-specific targets such as acetylcholine receptors in myasthenia gravis or insulin and glutamic acid decarboxylase in type 1 diabetes; and myelin components in multiple sclerosis.

Recognition of self-antigens is influenced by genetic factors affecting antigen presentation and tolerance, as well as mechanisms such as epitope spreading after tissue injury, molecular mimicry with pathogens, or exposure of cryptic antigens. Clinically, autoantibodies against self-antigens serve as diagnostic markers and can guide therapy in autoimmune diseases.