Peripheral tolerance

Peripheral tolerance is a mechanism by which the immune system prevents an immune response against self-antigens, thus preventing autoimmunity. It is one of two types of immune tolerance, the other being central tolerance. Peripheral tolerance occurs in the lymph nodes, spleen, and other peripheral lymphoid tissues.

Mechanisms of Peripheral Tolerance

Peripheral tolerance is achieved through several mechanisms, including anergy, immunological ignorance, regulatory T cells, and clonal deletion.

Anergy

Anergy is a state of unresponsiveness by T cells and B cells to the presence of antigen. This can occur when the antigen is presented without the necessary second signal, or when there is a high concentration of antigen.

Immunological Ignorance

Immunological ignorance occurs when the immune system does not recognize an antigen. This can occur when the antigen is sequestered from the immune system, or when the antigen is present at low levels.

Regulatory T Cells

Regulatory T cells (Tregs) are a subset of T cells that modulate the immune system, maintain tolerance to self-antigens, and prevent autoimmune disease.

Clonal Deletion

Clonal deletion is the removal of B cells and T cells that have reacted against self-antigens.

Clinical Significance

Defects in peripheral tolerance can lead to autoimmune diseases, where the immune system attacks the body's own tissues. Examples of such diseases include rheumatoid arthritis, type 1 diabetes, and multiple sclerosis.

See Also

• Central tolerance
• Autoimmunity
• Immunology