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Infection, immunity and repair > T cell activation and regulation > Flashcards

T cell activation and regulation Flashcards

1
Q

Why is it important to regulat T cell activity?

A

T cell activation is important to have adequate, rapid immune resopnse

IS must organise robust protection to any pathogen the host may encounter

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2
Q

What must the IS not do when tackling pathogen?

A

Should not target host proteins

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3
Q

What is the meaning of double-edged sword when it comes to the IS?

A

IS helps fight infection

Can do harm if it dysregulates -> autoimmunity

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4
Q

What is positive selection?

A

If you bind you survive

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5
Q

What is negative selection?

A

If you bind you die

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6
Q

How is the large range of TCR specificity created?

A

Shuffling of germline genes

Creates diversity

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7
Q

What is the downside of having large variety of TCRs?

A

Can generate TCRs targeting self-proetins

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8
Q

Describe the process of negative selection in the thymus

A

Thymus selects against self-targeting TCRs

T cells with most reactivity to own tissues are:

Killed by negative selection

Induced to differentiate into regulatory T cells

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9
Q

Thymus solves the issue of autoimmunity

TRUE or FALSE

A

FALSE

Thymus is not perfect

Cannot purge all autoimmune T cells from the system

Can only reduce the chances of autoimmunity

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10
Q

What two cells do T cells infuence?

A

Mature T cells exit the thymus and populate the periphery

These are very influencial

Influence B cell activation

Influence macrophage activation

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11
Q

Describe the concept of naive T cell recirculation

A

T cell diversity is generated through thymic selection

T cell now bare different specificities

When infected by a microbe only a few T cells bare the correct TCR to recognise antigen

Naive T cells recirculate lymph nodes to examine whether APCS have presented an antigen they recognise

Spend around 24 hours in a lymph node

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12
Q

What happens when pathogen invades the body?

A

Protein antigens are taken up by APCs

APCs go to the nearest lymph nodes to display it

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13
Q

How many hours do naive T cells stay in the lymph nodes to see if APCs present an antigen they recognise?

A

24 hours

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14
Q

What happens if T cells don’t recognise the peptides expressed on TCRs?

A

Move to the next lymph node

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15
Q

T cells can only recognise processed antigens presented on MHC in the form of peptides

TRUE or FALSE

A

TRUE

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16
Q

What are TCRs made up of?

A

Two polypeptide chains

17
Q

What do CD3 coreceptors do?

A

Transduces TCR derived signals into the cell

18
Q

Why can TCR not transduce sinals intracellularly?

A

Short domains

19
Q

Why do people not get equally sick when infected by the same pathogen?

A

MHC presenting the same antigen are different for different people

Some bind to antigens better

20
Q

What signals are needed for T cells to become activated?

A

TCR - respond to peptides presented by MHC

Costimulatory signal via CD 28 - binds to CD80/86 on AOCs

21
Q

What is CD 28?

A

A costimulatory receptor on CSM of T cells

22
Q

What does CD 28 bind to?

A

CD 80/86 on APCs

23
Q

What would happen if CD 28 did not bindd to CD 86 on APCs?

A

The interaction of T cells and APCs would be non-productive and lead to cell anergy

24
Q

What is another name for CD 80/86?

A

B 7

25
Q

B7 on APCs can be upregulated by molecules derived from microbes or inflammatory cytokines

TRUE or FALSE

A

TRUE

26
Q

What is anergy?

A

Lack of reaction by the body’s defense mechanisms to foreign substances

27
Q

What is CTLA-4?

A

Same as CD 28, but on Treg cells

Bind to B7 complex on APCs

28
Q

What happens when CTLA-4 binds to B7 complex on APCs?

A

Downregulation of immunity

Critical immune suppressor

29
Q

How does CTLA-4 suppress immunity?

A

Binds to B7 complex on APCs with higher affinity compared to T effector cells

30
Q

What happened to mice lacking CTLA-4?

A

Overactive immune systems

Huge spleens and lymph nodes

31
Q

What maintains homeostasis of the immune system?

A

Constant balance in the immune response between costimulation and coinhibition

Decides whether immune response is mounted or not

32
Q

What are the 4 suggested pathways by which CTLA-4 works?

A

Negative signalling - CTLA-4 transmits inhibitory signalling in T cells that express them

Ligand competition - CTLA-4 binds to costimulatory ligands with higher affinity that CD28

Influence adhesion/ motility - CTLA-4 removes B7 complexes on APCs

Reverse signalling through ligands

33
Q

How does ligand competition lead to a regulation of the immune response?

A

CTLA-4 binds to costimulatory ligands with higher affinity that CD28

So the T effector cells are unable to get costimulatory signals needed to activate the cells

Infection, immunity and repair (52 decks)

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