Self-tolerance

Definition

Self-tolerance is the ability of the immune system to recognize and tolerate the body's own cells and tissues while mounting an immune response against foreign invaders. This crucial mechanism helps prevent autoimmune diseases, where the immune system mistakenly attacks healthy cells, and maintains a balance in immune responses, allowing for efficient defense against pathogens without harming the host.

5 Must Know Facts For Your Next Test

1. Self-tolerance is developed during early immune cell maturation, especially in the thymus, where T-cells learn to identify self-antigens.
2. A breakdown in self-tolerance can lead to autoimmune disorders, such as rheumatoid arthritis or type 1 diabetes, where the body attacks its own cells.
3. There are two main types of self-tolerance: central tolerance, which occurs in the thymus and bone marrow, and peripheral tolerance, which happens outside these primary organs.
4. Regulatory T-cells are essential for maintaining self-tolerance, as they help suppress autoreactive cells that could cause harm.
5. Self-tolerance is vital for a healthy immune system; without it, the body would continually attack itself, leading to inflammation and tissue damage.

Review Questions

• How does the thymus contribute to the development of self-tolerance in T-cells?
  • The thymus plays a critical role in the maturation of T-cells, where they undergo a process called positive and negative selection. During positive selection, T-cells that can moderately bind to self-antigens are allowed to survive, while those that bind too strongly to self-antigens are eliminated during negative selection. This ensures that only those T-cells that can recognize foreign invaders without attacking self-tissues enter circulation, thereby promoting self-tolerance.
• What are the consequences of a failure in self-tolerance, and how do autoimmune diseases arise from this failure?
  • When self-tolerance fails, the immune system begins to target and destroy its own tissues, leading to autoimmune diseases. This breakdown can occur due to various factors including genetic predisposition, environmental triggers, or infections that mimic self-antigens. Conditions such as lupus or multiple sclerosis illustrate how this loss of self-tolerance results in chronic inflammation and damage to organs or systems within the body.
• Evaluate the significance of regulatory T-cells in maintaining self-tolerance within the immune system.
  • Regulatory T-cells are crucial for sustaining self-tolerance as they actively suppress autoreactive lymphocytes that could potentially harm healthy tissues. By secreting anti-inflammatory cytokines and directly inhibiting other immune cells, regulatory T-cells prevent excessive immune responses against self-antigens. Their role is particularly important in establishing peripheral tolerance, ensuring that even if some autoreactive cells escape central tolerance mechanisms, they do not initiate damaging reactions in peripheral tissues.

Related terms

Autoimmunity: A condition in which the immune system mistakenly attacks the body's own tissues, often due to a failure in self-tolerance.

Thymus:

An organ where T-cells mature and learn self-tolerance by distinguishing between self and non-self antigens.

Regulatory T-cells: A subset of T-cells that play a key role in maintaining self-tolerance by suppressing inappropriate immune responses.