L15: T Cell Development In The Thymus

Question 1

What are the main lymphocytes within the adaptive immune system

Answer 1

T lymphocytes

B lymphocytes

Question 2

Where are T lymphocytes derived from

Answer 2

From the thymus

Question 3

Where are B lymphocytes derived from

Answer 3

B cells in the bone marrow

Question 4

How do we get T lymphocytes from the thymus

Answer 4

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

Question 5

How do B cells recognise antigens

Answer 5

Can recognise the antigen directly or by immunoglobulin

Question 6

What is immunoglobulin also called

Answer 6

Antibodies

Question 7

What are immunoglobulin/antibodies

Answer 7

Receptors of B cells

Question 8

What are the chains of immunoglobulin

Answer 8

Heavy and light chains

Question 9

What are the 2 types of light chains

Answer 9

Kappa and lambda

Question 10

What do T cell receptors recognise

Answer 10

MHC

Question 11

What are the forms of T cell receptors

Answer 11

TCR beta and TCR alpha

TCR gamma and TCR delta

Question 12

Are T cell receptors specific i.e recognise different antigens

Answer 12

Yes

Question 13

What are the gene regions of T cell receptors

Answer 13

V
D
J
C

Question 14

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

Answer 14

V
D
J
C

Question 15

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

Answer 15

V
J
C

Question 16

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

Answer 16

Become rearranged

Question 17

How are gene segments of the regions rearranged

Answer 17

1) randomly gene segments from each region are chosen

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

Question 18

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

Answer 18

By:
Negative selection
Positive selection
Death by neglect

Question 19

What is negative selection

Answer 19

When lymphocytes target self antigens and therefore undergo apoptosis

Question 20

What is positive selection

Answer 20

When lymphocytes recognise the antigens so they survive

Question 21

What is death by neglect

Answer 21

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

Question 22

Where does selection occur for B cells

Answer 22

In the bone marrow

Question 23

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

Answer 23

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

Question 24

What is MHC present by to the T cell receptors

Answer 24

Antigen present cells

Question 25

Where does negative selection and positive selection occur for T cells

Answer 25

In the Thymus

Question 26

What are the 2 layers of the thymus

Answer 26

Cortex | Medulla

Question 27

What are the T cell types

Answer 27

CD4+ | CD8+

Question 28

What type of MHC does CD4+ T cell bind to

Answer 28

MHC class 2

Question 29

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

Answer 29

Class 1

Question 30

Which type of selection does the cortex of the thymus drive

Answer 30

Positive selection

Question 31

Which type of selection does the medulla of the thymus drive

Answer 31

Negative selection

Question 32

Name an example of a antigens presenting cell

Answer 32

Dendritic cells

Question 33

What happens in the thymus cortex for positive selection

Answer 33

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

Question 34

What happens in the Thymus medulla for negative selection

Answer 34

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

Question 35

What are the 2 types of T cell tolerance

Answer 35

Central tolerance | Peripheral tolerance

Question 36

What is central tolerance of T cells

Answer 36

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

Question 37

What is peripheral tolerance for

Answer 37

A backup mechanism for T cells that escape negative selection

Question 38

What is peripheral tolerance

Answer 38

Ignorance Anergy Cell death Regulatory T cell

Question 39

What is anergy

Answer 39

Switching off the T cell but not killing it

Question 40

What is regulatory T cells for

Answer 40

Regulating and controlling auto reactive reactions

Question 41

What are regulatory T cells produced

Answer 41

Thymus

Question 42

What is the role of regulatory T cells

Answer 42

Suppress auto reactive lymphocytes that escape negative selection

Question 43

What are the subset of T regulatory cells

Answer 43

CD4+ | CD25+

Question 44

Which factor expressions allow to give T regulatory cells

Answer 44

FOXP3

Question 45

How to T regulatory cells suppress cells

Answer 45

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

Question 46

What does AIRE stand for

Answer 46

Autoimmune regulator

Question 47

What is AIRE

Answer 47

A transcription factor

Question 48

What is AIRE expressed by

Answer 48

Medullary Thymic epithelial cells

Question 49

What does the AIRE transcription factor allow

Answer 49

Regulates promiscuous gene expression

Question 50

What is promiscuous gene expression

Answer 50

The Expression of lots of different gene expression in the thymus

Question 51

What does the promiscuous gene expression allow

Answer 51

Thymus to screen for self reactivity more effectively

Question 52

Give an example of promiscuous gene expression with AIRE

Answer 52

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

Question 53

What does AIRE protect against in terms of insulin

Answer 53

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

Question 54

How can FOXP3 deficiency occur

Answer 54

Due to mutation of IPEX

Question 55

If there is FOXP3 what does this lead to

Answer 55

No development of T regulatory cells and therefore autoimmunity

Question 56

How does AIRE deficiency occur

Answer 56

Mutation of APECED

Question 57

What does AIRE deficiency lead to

Answer 57

Prevention of promiscuous gene expression from occurring

Question 58

What are FOXP3 and AIRE deficiency called

Answer 58

Monoallelic autoimmune diseases

Question 59

What is Thymus aplasia

Answer 59

Thymus atrophy (shrinkage)

Question 60

What are the main category causes of thymus aplasia

Answer 60

Genetic | Natural

Question 61

What are the genetic causes of thymus aplasia

Answer 61

FOXN1 defiency | Complete di George syndrome

Question 62

What is complete di George syndrome

Answer 62

Children have no thymus

Question 63

What is FOX1N deficiency

Answer 63

Absence of thymus

Question 64

What are the natural causes of thymus aplasia

Answer 64

Age related thymus atrophy

Question 65

What happens to the thymus as we age

Answer 65

Declines in function

Question 66

What happens to the T cells in age related thymus atrophy

Answer 66

T cells decrease

Question 67

What is the treatment for di George syndrome

Answer 67

Thymus transplant