T Cells and B Cells: Structure and Function Overview

TCRs

T Cell Receptors that recognize antigens.

BCRs

B Cell Receptors that bind free antigens.

Gene Rearrangement

Process creating TCRs and BCRs in lymphocytes.

Thymus

Location where TCRs are generated.

Bone Marrow

Location where BCRs are generated.

MHC Molecules

Present processed antigens to TCRs.

Cytotoxic T Cells

Respond to antigens presented by MHC I.

Helper T Cells

Respond to antigens presented by MHC II.

Variable Antigen Specificity

Diversity in TCRs and BCRs from gene rearrangements.

Clonal Expansion

TCR genes undergo this after antigen recognition.

Polypeptide Chains

TCRs consist of α and β or γ and δ chains.

Complementarity-Determining Regions

CDRs are involved in antigen binding.

Antigen Binding Site

Formed by hypervariable regions of TCR chains.

CD4 Co-Receptors

Utilized by α:β T cells for antigen recognition.

CD8 Co-Receptors

Utilized by cytotoxic T cells for antigen recognition.

γ:δ T Cells

Less common T cell type with limited diversity.

TCR Complex

Includes TCR, CD3, and ζ-chain proteins.

Antigen Processing

Involves breaking down antigens for MHC presentation.

MHC Class I

Presents intracellular peptides to CD8 T cells.

MHC Class II

Presents extracellular peptides to CD4 T cells.

Peptide Length MHC I

Binds 8-10 amino acid peptides.

Peptide Length MHC II

Binds 13-25 amino acid peptides.

MHC Polymorphism

Affects T cell recognition and response.

Extracellular Pathogen Processing

Involves phagocytosis and MHC II presentation.

Intracellular Pathogen Processing

Involves proteasomes and MHC I presentation.

Degenerate Binding

MHC molecules bind various peptide sequences.

Proteasomes

Degrade proteins for antigen processing.

TAP

Transports peptides into ER for MHC I.

Chaperones

Assist in MHC I folding and peptide loading.

Bare Lymphocyte Syndrome

Deficiency in MHC Class I or II.

Invariant Chain

Prevents premature peptide binding to MHC II.

Cross-Presentation

Dendritic cells present extracellular antigens via MHC I.

MHC Gene Diversity

Highly polymorphic, no rearrangement occurs.

B-cell Maturation

Occurs in bone marrow, activation in lymphoid tissues.

Primary Lymphoid Tissues

Include bone marrow and thymus.

Secondary Lymphoid Tissues

Include spleen and lymph nodes.

Heavy Chain Rearrangement

First step in B-cell development.

Surrogate Light Chain

Tests heavy chain functionality in B cells.

Pre-B-Cell Receptor

Composed of heavy chain and surrogate light chain.

Allelic Exclusion

One allele expressed per B cell.

Immunoglobulin Expression

IgM expressed in immature B cells.

Burkitt's Lymphoma

Chromosomal translocation involving MYC gene.

B-1 Cells

Self-renewing B cells, no somatic hypermutation.

B-2 Cells

Produce memory cells and undergo somatic hypermutation.

Immature B Cells

Express only IgM before maturation.

Negative Selection

Removes self-reactive B cells.

Anergy

Unresponsive state of B cells to self-antigens.

Receptor Editing

Allows B cells to modify receptors.

Germinal Centers

Sites for B cell proliferation and maturation.

Affinity Maturation

Selection of B cells with high antigen affinity.