6. Lymphocyte development

Lymphopoiesis

The production of new lymphocytes.

Central lymphoid tissue

Tissues where lymphocyte development occurs, including bone marrow for B cells and thymus for T cells.

Common lymphoid progenitor (CLP)

A progenitor cell from which all lymphocytes derive.

Multipotent progenitor cells (MPP)

Cells that can produce both myeloid and lymphoid cells but can no longer self-renew.

IL-7

A cytokine essential for the growth and survival of developing B cells.

B cell receptor gene rearrangement

The process by which B cell receptor genes are rearranged during B cell development.

Pre-B receptor

A receptor formed by rearranged heavy chain pairing with surrogate light chains, providing signals necessary for B cell development.

Allelic exclusion

The process by which only one allele of a gene is expressed, while the other is silenced.

Immature B cells

B cells that have not yet completed development and are tested for autoreactivity.

Receptor editing

The process by which self-reactive B cells produce new receptors to change their specificity.

Anergy

A permanent state of unresponsiveness to antigens.

Transitional B cells

Stages of B cells (T1 and T2) in the spleen that are crucial for maturation.

BAFF

A B cell survival factor produced by follicular dendritic cells.

Follicular B cells

The major population of B cells residing in the follicles of secondary lymphoid organs.

Natural antibodies

Antibodies produced by B-1 B cells that do not require T cell help and respond to carbohydrate antigens.

Thymocyte

Developing T cells in the thymus.

Notch1 receptor

A receptor that aids in the commitment of progenitor cells to the T cell lineage.

Positive selection

The process by which thymocytes that recognize self-peptide:self-MHC complexes are rescued from apoptosis.

Negative selection

The elimination of thymocytes that react strongly to self-antigens.

Double positive (DP) thymocytes

Thymocytes that express both CD4 and CD8 co-receptors.

Sphingosine 1-phosphate (S1P)

A signaling molecule that helps draw mature T cells out of the thymus.

CD62L

A lymph node homing receptor facilitating naïve T cell localization to peripheral lymphoid organs.

γδ T cells

A subset of T cells that arise in distinct phases during development.

Thymic medulla

The area of the thymus where the final maturation of T cells occurs.

Chemokine CXCL12

A chemokine necessary for retaining developing B cells in the bone marrow.

Thymic stroma-derived lymphopoietin (TSLP)

A factor that resembles IL-7 and is involved in B cell development.

Cell adhesion molecules (CAM)

Proteins required for retaining developing B cells within the bone marrow.

E2A and EBF

Transcription factors that drive rearrangement of immunoglobulin genes during B cell development.

Anergy mechanisms

Methods by which autoreactive T cells are prevented from responding to self-antigens in the periphery.

Surrogate light chains

Invariant proteins that pair with the heavy chain to form the pre-B receptor.

MHC molecules

Molecules that present peptides to T cells and are crucial for positive and negative selection.

Thymectomy

Surgical removal of the thymus, leading to T cell deficiency.

Marginal zone B cells

A minor population of B cells found in the spleen.

Self-antigens

Antigens originating from the body's own tissues.

Fetal liver

A site of origin for B-1 B cells during embryonic development.

Clonal deletion

The process by which self-reactive B cells are eliminated.

Cortical stroma

The outer region of the thymus where most T cell development occurs.

Co-receptor specificity

The determination of CD4 or CD8 expression based on TCR-MHC interactions during positive selection.

Peripheral tolerance

The state of self-reactive B cells that encounter autoantigens after leaving the bone marrow.

Thymic epithelial cells

Cells that provide signals necessary for T cell development.

Thymocyte apoptosis

The programmed cell death experienced by non-selected +ve or -ve T cells.

Transcription factors in T cell development

Proteins that regulate the expression of genes required for T cell maturation.