T-Lymphocytes and Antigen Recognition

Question 1

What type of pathogen do T-Cells combat?

Answer 1

Intracellular, as antibodies can only attack extracellular pathogens

Question 2

What does the T-cell receptor detect?

Answer 2

Antigen presented on MHC molecule of infected cell

Question 3

What CD do all T-cells express?

Answer 3

CD3

Question 4

What do CD4 receptors do?

Answer 4

Recognise antigens on MHC class II

Question 5

What cells have CD4 receptors?

Answer 5

T helper cells

Question 6

What do CD8 receptors do?

Answer 6

Recognise antigens on MHC class I molecules

Question 7

What cells express CD8 receptors?

Answer 7

Cytotoxic T lymphocytes

Question 8

What do CD3 molecules do, and what are they a part of?

Answer 8

Deliver signal to T-cell once antigen has been recognised.

Part of the T cell receptor (TCR)

Question 9

What do CD4 cells do?

Answer 9

Secret cytokines to recruit effector cells and activate macrophages

Question 10

What do CD8 cells do?

Answer 10

Are cytotoxic and kill target cells by secreting cytokines to induce apoptosis

Question 11

What receptors do T-cells have when they arrive at the thymus (immature)

Answer 11

CD4-
CD8-
TCR-

Question 12

When the TCR has been developed, what receptors are present on a T cell?

Answer 12

CD4+
CD8+
TCR+

Question 13

How is a CD co-receptor removed?

Answer 13

By exposure of T-cell to MHC class I/II, determining the CD to be removed.

Question 14

What percentage of T-cells survive selection?

Answer 14

5%

Question 15

What does the Major Histocompatibility complex do?

Answer 15

Display sample of internal cell components for immune recognition.
Markers of self/health; continuously present

Question 16

What are the 4 regions of MHC molecules?

Answer 16

Cytoplasmic
Transmembrane
Immunoglobulin like
Peptide binding

Question 17

What size Peptides do each MHC class present?

Answer 17

MHC Class I: 8-10 amino acids

MHC Class II: >13 amino acids

Question 18

What chains does an MHC Class I molecule have?

Answer 18

Alpha 1 Alpha 2
Beta 2 Alpha 3
(Beta 2 is microglobulin)

Question 19

What chains does an MHC Class II molecule have?

Answer 19

Alpha 1 Beta 1

Alpha 2 Beta 2

Question 20

What are the differences between MHC Classes I/II?

Answer 20

Class II has 2 cytoplasmic regions

Polypeptide chains are the same length in Class II

Question 21

Which cells express MHC Class I?

Answer 21

All nucleated cells.

Levels may fluctuate during infection or by cytokines

Question 22

Which cells express MHC Class II?

Answer 22

Professional antigen presenting cells

Question 23

What are endogenous antigens?

Answer 23

Antigens that come from inside cells - use CD8 Class I restricted T-cells

Question 24

What are Exogenous antigens?

Answer 24

Antigens from outside cells (e.g. phagocytotic and presented antigens) - Use CD4 Class II restricted T-cells

Question 25

What are effector T cells?

Answer 25

Cells that have encountered antigen, proliferated and differentiated into cells that participate in host defence

Question 26

What happens to the effector pool after an infection is cleared?

Answer 26

Effector pool contracts to memory pool, as cells die if not signalled to stay alive

Question 27

What are MHC’s called in humans, and where on the genome are they coded for?

Answer 27

Human Leukocyte Antigen

Chromosome 6

Question 28

What gene with relation to the immune system is regarded as the most polymorphic?

Answer 28

MHC gene

Over 4200 HLA alleles

Question 29

What is the main antigen presenting cell?

Answer 29

Dendritic cell

Question 30

What is the 3 signal licensing model?

Answer 30

1. Antigen recognition - T-cell activation
2. Co-stimulation - surface molecules on Dendritic cells need to enter TCR to activate
3. Cytokines - produced by D cells activate T cells

Question 31

What is the function of CD8 Cytotoxic T-cells?

Answer 31

To kill infected cells by recognising MHC I peptide

Question 32

What are the 2 ways a Cytotoxic T-cell can kill?

Answer 32

1. Perforin molecules polymerise to form pores to allow granzymes to be injected into cell to drive apoptosis
2. Fas ligands interact with target cell Fas receptors to induce cell death

Question 33

Why are Cytotoxic T-cells described as serial killers?

Answer 33

As they won’t stop at one cell, they’ll kill as many as they can

Question 34

What happens to granules in a CD8 T-cell when a pathogen is detected?

Answer 34

They polarise towards the pathogen side of the cell

Question 35

What are the 4 main functions of T helper cells?

Answer 35

Macrophage activation
Delayed type hypersensitivity response
B cell activation
Regulation

Question 36

What disease is charecterised by a lack of T helper cells?

Answer 36

HIV/AIDs

Question 37

How are subsets of T helper cells defined?

Answer 37

By the cytokines they release

Question 38

Name 4 subtypes of T helper cell, and what they do:

Answer 38

T helper 1: Boost intracellular immune response. Activate macrophages
T helper 2: Boost anti-multicellular response. Activate B-cells
Follicular helper T cells: Essential for generation of isotope-switched antibodies
T regulatory cells: Maintain tolerance of self-antigens, regulate activation/effector functions of other T-cells

Question 39

What do Th17 cells do?

Answer 39

Talk to neutrophils to kill bacteria

Question 40

What are the two phases of delayed type hypersensitivity?

Answer 40

Sensation phase: Dendritic cell takes up antigen and presents to T-cells. Memory pool built up
Effector phase: Second exposure severe response in macrophage mediated response and mast cell degranulation.

Question 41

What is different between B cell and T cell memory?

Answer 41

T-cells don’t undergo affinity maturation - Don’t improve over time

Question 42

What is T-cell exhaustion?

Answer 42

Over time, CD8 pools contracts to prevent excess damage; problomatic in cancer, HIV where infection has not cleared.