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IIH > L15: T Cell Development In The Thymus > Flashcards

L15: T Cell Development In The Thymus Flashcards

1
Q

What are the main lymphocytes within the adaptive immune system

A

T lymphocytes

B lymphocytes

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2
Q

Where are T lymphocytes derived from

A

From the thymus

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3
Q

Where are B lymphocytes derived from

A

B cells in the bone marrow

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4
Q

How do we get T lymphocytes from the thymus

A

T lymphocyte progenitors are made in the bone marrow then migrate to the thymus to mature into T cells.

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5
Q

How do B cells recognise antigens

A

Can recognise the antigen directly or by immunoglobulin

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6
Q

What is immunoglobulin also called

A

Antibodies

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7
Q

What are immunoglobulin/antibodies

A

Receptors of B cells

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8
Q

What are the chains of immunoglobulin

A

Heavy and light chains

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9
Q

What are the 2 types of light chains

A

Kappa and lambda

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10
Q

What do T cell receptors recognise

A

MHC

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11
Q

What are the forms of T cell receptors

A

TCR beta and TCR alpha

TCR gamma and TCR delta

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12
Q

Are T cell receptors specific i.e recognise different antigens

A

Yes

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13
Q

What are the gene regions of T cell receptors

A

V
D
J
C

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14
Q

What are the specific gene regions of TCR beta and gamma and immunoglobulin heavy chain

A

V
D
J
C

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15
Q

What are the specific gene regions of TCR alpha, delta and immunoglobulin light chain

A

V
J
C

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16
Q

What happens to these gene regions to create diversity of the receptors

A

Become rearranged

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17
Q

How are gene segments of the regions rearranged

A

1) randomly gene segments from each region are chosen

2) gene segments therefore get rearranged to form a protein of a receptor

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18
Q

If we have random receptor cells being generated due to gene rearrangement how do avoid lymphocytes recognises our own body tissue i.e autoimmune disease

A

By:
Negative selection
Positive selection
Death by neglect

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19
Q

What is negative selection

A

When lymphocytes target self antigens and therefore undergo apoptosis

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20
Q

What is positive selection

A

When lymphocytes recognise the antigens so they survive

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21
Q

What is death by neglect

A

When lymphocytes don’t recognise foreign or self antigens so they are left alone i.e death by neglect

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22
Q

Where does selection occur for B cells

A

In the bone marrow

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23
Q

How does negative and positive selection occur in the bone marrow for B cells

A

1) B cell receptors on an immature B cells binds to self antigen on bone marrow stromal cell
2) if there is no recognition of the self antigen by the receptors the immature B cells survives and matures on for positive selection
3) if however there is recognition of self antigen of bone marrow cells, immature B cells apoptosis and this is negative selection

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24
Q

What is MHC present by to the T cell receptors

A

Antigen present cells

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25
Q

Where does negative selection and positive selection occur for T cells

A

In the Thymus

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26
Q

What are the 2 layers of the thymus

A

Cortex

Medulla

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27
Q

What are the T cell types

A

CD4+

CD8+

28
Q

What type of MHC does CD4+ T cell bind to

A

MHC class 2

29
Q

What type of MHC class does CD8+ T cell bind to

A

Class 1

30
Q

Which type of selection does the cortex of the thymus drive

A

Positive selection

31
Q

Which type of selection does the medulla of the thymus drive

A

Negative selection

32
Q

Name an example of a antigens presenting cell

A

Dendritic cells

33
Q

What happens in the thymus cortex for positive selection

A

1) if T cells binds to MHC they undergo positive selection and move into the medulla
2) if developing T cells cannot bind to MHC it undergoes death by neglect

34
Q

What happens in the Thymus medulla for negative selection

A

1) if T cells bind strongly to MHC they undergone Negative selection
2) if T cells do not bind strongly to MHC they survive and mature further

35
Q

What are the 2 types of T cell tolerance

A

Central tolerance

Peripheral tolerance

36
Q

What is central tolerance of T cells

A

This is the positive and negative selection that occurs in the thymus

37
Q

What is peripheral tolerance for

A

A backup mechanism for T cells that escape negative selection

38
Q

What is peripheral tolerance

A

Ignorance
Anergy
Cell death
Regulatory T cell

39
Q

What is anergy

A

Switching off the T cell but not killing it

40
Q

What is regulatory T cells for

A

Regulating and controlling auto reactive reactions

41
Q

What are regulatory T cells produced

A

Thymus

42
Q

What is the role of regulatory T cells

A

Suppress auto reactive lymphocytes that escape negative selection

43
Q

What are the subset of T regulatory cells

A

CD4+

CD25+

44
Q

Which factor expressions allow to give T regulatory cells

A

FOXP3

45
Q

How to T regulatory cells suppress cells

A

Secrete cytokine that dampen down T cell responses
Compete for T cell growth factors such as IL2
Contact dependent

46
Q

What does AIRE stand for

A

Autoimmune regulator

47
Q

What is AIRE

A

A transcription factor

48
Q

What is AIRE expressed by

A

Medullary Thymic epithelial cells

49
Q

What does the AIRE transcription factor allow

A

Regulates promiscuous gene expression

50
Q

What is promiscuous gene expression

A

The Expression of lots of different gene expression in the thymus

51
Q

What does the promiscuous gene expression allow

A

Thymus to screen for self reactivity more effectively

52
Q

Give an example of promiscuous gene expression with AIRE

A

AIRE allows insulin gene to be expressed in the thymus so that T cells developing recognise insulin and undergo negative selection

53
Q

What does AIRE protect against in terms of insulin

A

Diabetes because we are destroying the cells that will kill beta cells in the pancreas

54
Q

How can FOXP3 deficiency occur

A

Due to mutation of IPEX

55
Q

If there is FOXP3 what does this lead to

A

No development of T regulatory cells and therefore autoimmunity

56
Q

How does AIRE deficiency occur

A

Mutation of APECED

57
Q

What does AIRE deficiency lead to

A

Prevention of promiscuous gene expression from occurring

58
Q

What are FOXP3 and AIRE deficiency called

A

Monoallelic autoimmune diseases

59
Q

What is Thymus aplasia

A

Thymus atrophy (shrinkage)

60
Q

What are the main category causes of thymus aplasia

A

Genetic

Natural

61
Q

What are the genetic causes of thymus aplasia

A

FOXN1 defiency

Complete di George syndrome

62
Q

What is complete di George syndrome

A

Children have no thymus

63
Q

What is FOX1N deficiency

A

Absence of thymus

64
Q

What are the natural causes of thymus aplasia

A

Age related thymus atrophy

65
Q

What happens to the thymus as we age

A

Declines in function

66
Q

What happens to the T cells in age related thymus atrophy

A

T cells decrease

67
Q

What is the treatment for di George syndrome

A

Thymus transplant

IIH (26 decks)

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