Podcast
Questions and Answers
What are the 3 broad classes of T cells?
What are the 3 broad classes of T cells?
How many antigen binding sites does a T-cell receptor have?
How many antigen binding sites does a T-cell receptor have?
One
How many hypervariable regions make up the antigen binding site of a T-cell receptor?
How many hypervariable regions make up the antigen binding site of a T-cell receptor?
Six
What is the function of the T cell receptor constant regions?
What is the function of the T cell receptor constant regions?
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What processes are responsible for generating T cell receptor diversity?
What processes are responsible for generating T cell receptor diversity?
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What gene segments make up the α-chain variable region?
What gene segments make up the α-chain variable region?
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What type of antigen do T cells recognize?
What type of antigen do T cells recognize?
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What is the functional difference between MHC class I and MHC class II molecules?
What is the functional difference between MHC class I and MHC class II molecules?
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Which cell types express MHC class I molecules?
Which cell types express MHC class I molecules?
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Which T cell co-receptor binds to MHC class I?
Which T cell co-receptor binds to MHC class I?
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What is cross-presentation?
What is cross-presentation?
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How many different class I and II molecules does each person have for presenting antigens?
How many different class I and II molecules does each person have for presenting antigens?
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What does polymorphic mean in the context of MHC genes?
What does polymorphic mean in the context of MHC genes?
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Why is it beneficial to have a large number of different MHC alleles?
Why is it beneficial to have a large number of different MHC alleles?
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How do only 12 MHC molecules in each person present such a broad range of antigens?
How do only 12 MHC molecules in each person present such a broad range of antigens?
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What is the peptide binding motif?
What is the peptide binding motif?
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What is MHC restriction?
What is MHC restriction?
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Study Notes
T Cell Classes
- Cytotoxic T cells are classified as CD8 T cells.
- Helper T cells and Regulatory T cells are classified as CD4 T cells.
T Cell Receptor Components
- T cell receptors (TCRs) feature one antigen binding site formed by variable regions of α and β chains.
- The antigen binding site comprises 6 hypervariable regions—3 in the α chain and 3 in the β chain.
T Cell Receptor Structure
- Constant regions of TCRs provide structural support and anchor the receptor to the membrane.
- T cell receptor diversity arises from somatic recombination, junctional diversity, and random α/β chain pairing.
Gene Segments in T Cell Receptors
- The α-chain variable region is formed from V and J gene segments.
- The β-chain variable region consists of V, D, and J gene segments.
- Constant regions of TCRs are not composed of gene segments.
Antigen Recognition
- T cells specifically recognize peptide antigens that are presented on MHC molecules.
MHC Molecules
- MHC class I molecules present antigens from cytosolic sources to CD8 T cells.
- MHC class II molecules present antigens from extracellular sources to CD4 T cells.
Expression of MHC Molecules
- Almost all body cells express MHC class I molecules, enabling them to present antigens to CD8 T cells.
- Only antigen-presenting cells (APCs), like dendritic cells, macrophages, and B cells, express MHC class II molecules.
T Cell Co-receptors
- CD8 co-receptor binds to MHC class I molecules.
- CD4 co-receptor binds to MHC class II molecules.
Cross-Presentation
- Cross-presentation occurs in dendritic cells when they present extracellular antigen on MHC class I to activate CD8 T cells, despite not being infected by that antigen.
MHC Molecule Variability
- Each individual has 6 MHC class I and 6 MHC class II molecules, originating from both parents.
- MHC genes are highly polymorphic, having numerous alleles across the population.
Importance of MHC Polymorphism
- A diverse range of MHC alleles enhances the population's ability to present a wide array of antigens, addressing emerging pathogens and diseases.
MHC Binding Specificity
- MHC molecules exhibit promiscuous binding specificity, allowing them to present a broad spectrum of peptide antigens.
- The peptide binding motif, defined by specific anchor residues, determines which antigens a particular MHC molecule can bind.
Definition of MHC Restriction
- MHC restriction refers to the specificity of T cell receptors for both antigens and the corresponding MHC molecule necessary for recognition.
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Description
Test your knowledge of T-cell receptors and MHC molecules with these flashcards. The quiz covers the different classes of T cells, their definitions, and key components of the T cell receptor. Perfect for students studying immunology.
