Adaptive immune responses: T cells

Question 1

What is the difference between B and T cells when it comes to their specialisation?

Answer 1

B cells stay and specialise in the bone marrow

T cells migrate to the thymus in order to specialise

Question 2

Where is the thymus located?

Answer 2

In the thoracic cavity

Next to the heart

Question 3

Why is the thymus especially important in children?

Answer 3

Most T cells develop during childhood

Question 4

Why are TCRs and BCRs specific?

Answer 4

Operate through a lock and key model

Question 5

Why is clonal expansion important?

Answer 5

The population of T cells with a specific TCR is low

Cells which are useful in fighting the microbes are expanded

This clonal expansion forms T cells with the same TCR which is relevant to the infection

Question 6

What is one reason why adaptive immunity takes longer than innate immunity?

Answer 6

The T cells with the specific TCR to the antigen have to clonally expand

Question 7

What are the 4 features of the adaptive immunity?

Answer 7

Specificity

Diversity

Memory

Clonal expansion

Question 8

What is the functional significance of the adaptive immune system being specific?

Answer 8

Ensures that distinct antigens elicit specific responses

Question 9

What is the functional significance of the adaptive immune system being diverse?

Answer 9

Enables the immune system to respond to a large variety of antigens

Question 10

What is the functional significance of the adaptive immune system having memory?

Answer 10

Leads to enhanced immune response to repeated exposures to the same antigens

Question 11

What is the functional significance of the adaptive immune system clonally expanding?

Answer 11

Increases the small number of antigen-specific lymphocytes from a small number of naive lymphocytes

Question 12

What percentage of T cells express TCRab?

Answer 12

90%

Question 13

What are the T cells which express TCRab split into?

Answer 13

CD4 cells

CD8 cells

Question 14

What do T cells which don’t have TCRab express instead?

Answer 14

TCRyd (gamma, delta)

Question 15

Why does the T cell receptor need a CD3 complex?

Answer 15

The TCR is not embedded in the T cell membrane deeply enough to transduce a signal to the cell

T CD3 molecules therefore do the signalling for the TCR

Question 16

What is CD3?

Answer 16

Complex of invariant chains which allows for the TCR signal to be transduced into the cell following binding with antigens

Question 17

Is the CD3 signal enough for a response to be evoked upon binding with antigens?

Answer 17

No

Requires another costimulatory receptor

The most important is CD28

Question 18

What is signal 1?

Answer 18

CD3 intracellular pathway activation

Question 19

What is signal 2?

Answer 19

CD28 intracellular pathway activation

Question 20

What happens to the T cell if it just receives signal 1?

Answer 20

Does not become activated

Becomes anergic

Question 21

How does the T cell become activated?

Answer 21

Through obtaining both signal 1 and signal 2

Question 22

What is required for the costimulatory receptors on T cells to become activated?

Answer 22

APCs need to have ligands for costimulation

These form the B7 complex

Question 23

What forms the B7 complex?

Answer 23

CD80 and CD86

Question 24

What does the nature of the immune response depend on?

Answer 24

The type of T cell which is activated

Question 25

Which cells do CD8 T cells kill?

Answer 25

Infected cells Cancer cells

Question 26

Which MHC molecule do CD8 T cells interact with?

Answer 26

MHC I

Question 27

Through which mechanisms do CD8 T cells kill their targets?

Answer 27

Cytotoxic granules containing perforin and granzyme Binding to death receptors on target cells like Fas

Question 28

Describe how CD8 T cells kill their targets through granzymes

Answer 28

Perforin form pores which facilitate the entry of granzymes Granzymes cause apoptosis and cell death

Question 29

Describe how CD8 T cells kill their targets through death receptors

Answer 29

CTL can bind to death receptors on target cells Including death receptor FasL Upregulation of the ligand on CD8 T cells will kill the cell expressing FasR

Question 30

Describe the different types of CD4 T cells

Answer 30

Helper cells Regulatory cells

Question 31

What is the role of CD4 regulatory T cells?

Answer 31

Inhibitory Play an important role in autoimmunity Suppress immune responses

Question 32

What are 3 different subclasses of T helper cells

Answer 32

Th1 Th2 Th17

Question 33

What is the marker for Th1 cells?

Answer 33

IFN y

Question 34

What is the target cell for IFNy?

Answer 34

Macrophages

Question 35

What type of pathogen do Th1 cells respond to?

Answer 35

Intracellular pathogens

Question 36

What are the markers for Th2 cells?

Answer 36

IL-4 Il-5 IL-13

Question 37

What is the target cell for Th2 cells?

Answer 37

Eosinophils

Question 38

Which pathogen do Th2 cells respond to?

Answer 38

Parasites

Question 39

What are the markers for Th17 cells?

Answer 39

IL-17 IL-22

Question 40

What is the target cell for Th17 cells?

Answer 40

Neutrophils

Question 41

Which pathogens do Th17 cells respond to?

Answer 41

Extracellular pathogens

Question 42

How do the cells of the immune system travel around in the body?

Answer 42

Blood Lymph vessels

Question 43

How are the collections of cells in the lymph nodes connected?

Answer 43

Through lymphatics

Question 44

Apart from clonal expansion, what is another way T cells compensate for the low population of T cells with specific receptors?

Answer 44

Travel throughout the body to find microbes

Question 45

Can T cells respond to antigen straight away like B cells?

Answer 45

No They need an antigen presentation stage This is why the humoral immune response comes before the cellular immune response

Question 46

What is another name for the immune system under the control of T cells?

Answer 46

Cellular immune response