Immunogly Chp 7

Cortex

The outermost region of the thymus containing immature T cells undergoing differentiation.

Medulla

The inner region of the thymus, containing mature thymocytes and specialized epithelial cells.

Thymic Epithelial Cells

Cells that provide structural support and produce cytokines essential for T-cell maturation.

Dendritic Cells

Cells that present antigens to thymocytes during the selection process.

Macrophages

Cells that help eliminate apoptotic thymocytes that fail selection.

Blood-Thymus Barrier

A structure that protects developing thymocytes from external antigens.

Positive Selection

Ensures T cells can recognize MHC molecules for immune response.

Negative Selection

Eliminates autoreactive T cells to promote self-tolerance.

Lineage Commitment

Directs T cells to differentiate into CD4+ or CD8+ cells.

AIRE

Enables expression of tissue-specific self-antigens in the thymus.

Tregs

CD4+ T cells that maintain immune tolerance and prevent autoimmunity.

DN T Cell Progenitor Stage

The stage where T cell progenitors are double-negative and lack CD4 and CD8.

Commitment to T Cell Lineage

Notch signaling directs progenitor cells to the T cell lineage.

TCR β-Chain Gene Rearrangement

The rearrangement of the TCR β-chain through VDJ recombination.

Pre-TCR Expression

Occurs when a functional TCRβ chain combines with a pre-Tα chain.

TCR α-Chain Rearrangement

The rearrangement of the TCR α-chain after TCR β-chain formation.

Selection and Maturation

Positive and negative selection processes that determine T-cell functionality.

Pre-TCR

A receptor composed of a rearranged TCR β-chain and a pre-Tα chain.

TCR

The mature receptor composed of TCR α and β chains capable of recognizing antigens.

CD4+CD8+

Double-positive thymocytes expressing both CD4 and CD8 co-receptors.

CD4+

Single-positive T cells that assist other immune cells.

CD8+

Single-positive T cells that eliminate infected or cancerous cells.

Hematopoietic stem cells (HSCs)

Cells in the bone marrow that give rise to T cell progenitors.

Common Lymphoid Progenitors (CLPs)

Progenitors that migrate to the thymus as double-negative thymocytes.

VJ recombination

The process for rearranging the TCR α-chain.

Thymocyte

Developing T cells within the thymus.

CD34+

Marker expressed by T cell progenitors entering the thymus.

Thymic epithelial cells (mTECs)

Specialized cells in the medulla that help in negative selection.

Hassall's corpuscles

Clusters of degenerating epithelial cells in the thymic medulla.

Cytokines

Proteins produced by thymic epithelial cells essential for T cell maturation.

Surrogate α-chain

The pre-Tα chain paired with TCRβ in pre-TCR formation.

Autoreactive T cells

T cells that react against the body’s own tissues.

Functional competence

The ability of mature T cells to appropriately respond in immune functions.

CD45RA

Marker for migration to secondary lymphoid organs.

CCR7

Chemokine receptor important for T cell homing to lymphoid tissues.

Immunoregulatory receptors

Surface markers that influence T cell development and function.

Thymic selection process

The steps of positive and negative selection that thymocytes undergo.

ThPOK

Transcription factor involved in CD4+ T cell lineage commitment.

Runx3

Transcription factor involved in CD8+ T cell lineage commitment.

Self-tolerance

The ability of the immune system to avoid attacking self-antigens.

Diversity of T cells

A variety of T cell responses generated through positive and negative selection.

Thymic blood vessels

Vessels that facilitate the entry of T cell progenitors into the thymus.

Early thymocyte development

Phases where T cells mature in the thymus.

Spleen

An organ where mature T cells migrate for immune response activation.

Bone marrow

T cell progenitors originate here before migrating to the thymus.

Chronic inflammation

A prolonged inflammatory response that can affect tissue integrity.

Autoimmune diseases

Disorders arising from a malfunctioning immune response against self.