Thymic selection

Definition

Thymic selection is the process by which T cells mature and undergo positive and negative selection in the thymus to ensure self-tolerance and proper immune response. This ensures that only T cells capable of recognizing antigens presented by MHC molecules survive.

5 Must Know Facts For Your Next Test

1. Positive selection occurs in the thymic cortex, where T cells that recognize self-MHC molecules receive survival signals.
2. Negative selection happens in the thymic medulla, eliminating T cells that bind too strongly to self-antigens presented by MHC.
3. Thymic epithelial cells play a crucial role in presenting self-antigens during both positive and negative selection.
4. Failure of thymic selection can lead to autoimmune disorders due to the survival of self-reactive T cells.
5. Approximately 98% of developing T cells do not survive thymic selection and undergo apoptosis.

Review Questions

• What are the two main processes involved in thymic selection?
• Why is negative selection important for preventing autoimmune diseases?
• Where does positive selection occur within the thymus?

Related terms

T Lymphocytes:

A type of white blood cell that plays a central role in cellular immunity.

MHC Molecules:

Major Histocompatibility Complex proteins that present peptide antigens to T cells.

Autoimmunity: An inappropriate immune response against self-antigens leading to tissue damage.