Anergy

Definition

Anergy is a state of unresponsiveness in immune cells, particularly T cells, where they fail to react to an antigen despite being exposed to it. This phenomenon is crucial for maintaining immune tolerance, preventing inappropriate immune responses against self-antigens, and ensuring that the immune system does not attack the body's own tissues. Anergy acts as a mechanism of peripheral tolerance, helping to maintain homeostasis within the immune system.

5 Must Know Facts For Your Next Test

1. Anergy can occur when T cells recognize antigens without receiving the necessary co-stimulatory signals from antigen-presenting cells.
2. In a state of anergy, T cells remain alive but become functionally inactive, preventing them from proliferating or producing cytokines in response to an antigen.
3. Anergy is distinct from clonal deletion, which involves the permanent removal of autoreactive T cells from the immune repertoire.
4. The induction of anergy is a critical component of peripheral tolerance mechanisms that prevent autoimmune diseases.
5. Certain cytokines and signaling pathways, such as those involving CTLA-4 and PD-1, are involved in promoting anergy in T cells.

Review Questions

• How does anergy contribute to the maintenance of immune tolerance and prevent autoimmune reactions?
  • Anergy contributes to immune tolerance by rendering T cells unresponsive to antigens they encounter without the necessary co-stimulatory signals. This unresponsiveness ensures that potentially autoreactive T cells do not initiate an immune response against self-antigens, thereby preventing autoimmunity. By maintaining a population of anergic T cells, the immune system can avoid damaging its own tissues while still being capable of responding to foreign antigens when properly activated.
• Discuss the role of co-stimulatory signals in the activation of T cells and how their absence leads to anergy.
  • Co-stimulatory signals are essential for full activation of T cells. When a T cell's receptor binds to an antigen on an antigen-presenting cell, it requires additional signals from co-stimulatory molecules, such as CD28 binding to CD80/CD86. If these signals are absent, the T cell enters a state of anergy instead of becoming activated. This mechanism acts as a checkpoint that prevents inappropriate or excessive activation of T cells, thereby contributing to peripheral tolerance.
• Evaluate the implications of anergy for therapeutic interventions in autoimmune diseases and cancer.
  • Anergy has significant implications for developing therapies targeting autoimmune diseases and cancer. In autoimmune conditions, enhancing anergic pathways may help restore tolerance and prevent tissue damage by keeping autoreactive T cells in check. Conversely, in cancer therapy, overcoming tumor-induced anergy can improve anti-tumor immunity by reactivating T cells that have become unresponsive to tumor antigens. Understanding the mechanisms regulating anergy can lead to novel strategies for manipulating immune responses in various disease contexts.

Related terms

Tolerance: The ability of the immune system to recognize and accept self-antigens without mounting an immune response against them.

Regulatory T cells (Tregs):

A specialized subset of T cells that play a critical role in maintaining immune tolerance by suppressing excessive immune responses.

Clonal deletion: A process during T cell development where autoreactive T cells that strongly recognize self-antigens are eliminated to prevent autoimmunity.