Immunology Chapter 5 Flashcards

Questions and Answers

What are the 3 broad classes of T cells?

Memory T cells

Helper T cells (correct)

Cytotoxic T cells (correct)

Regulatory T cells (correct)

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?

Six

What is the function of the T cell receptor constant regions?

Structural support and anchoring to the membrane Signup and view all the answers

What processes are responsible for generating T cell receptor diversity?

Somatic recombination, junctional diversity, random association of α and β chains Signup and view all the answers

What gene segments make up the α-chain variable region?

V and J Signup and view all the answers

What type of antigen do T cells recognize?

Peptide Signup and view all the answers

What is the functional difference between MHC class I and MHC class II molecules?

MHC class I presents antigens from the cytosol to CD8 T cells, while MHC class II presents antigens from outside the cell to CD4 T cells. Signup and view all the answers

Which cell types express MHC class I molecules?

Most cells in the body Signup and view all the answers

Which T cell co-receptor binds to MHC class I?

CD8 Signup and view all the answers

What is cross-presentation?

It is the process where dendritic cells present extracellular antigens on MHC class I molecules to activate CD8 T cells. Signup and view all the answers

How many different class I and II molecules does each person have for presenting antigens?

6 MHC class I and 6 MHC class II molecules Signup and view all the answers

What does polymorphic mean in the context of MHC genes?

It means that a gene has many different alleles. Signup and view all the answers

Why is it beneficial to have a large number of different MHC alleles?

It increases the range of peptide antigens that can be presented. Signup and view all the answers

How do only 12 MHC molecules in each person present such a broad range of antigens?

MHC molecules have promiscuous binding specificity, allowing them to bind to many different peptide antigens. Signup and view all the answers

What is the peptide binding motif?

KVN (Lys-Val-Asn) Signup and view all the answers

What is MHC restriction?

It means that a T-cell receptor is highly specific for both the antigen and the MHC molecule. Signup and view all the answers

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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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.