Lecture 3C- T-Cell Development

Question 1

Where are T cells derived from?

Answer 1

The thymus gland

Question 2

What is the purpose of positive selection in T cell development?

Answer 2

To ensure T cells recognize self-MHC molecules

Question 3

What is an immature T-cell called?

Answer 3

thymocyte

Question 4

Is the thymus gland considered a primary or secondary lymphatic organ?

Answer 4

primary

Question 5

CD4 T cells are also known as _____ T cells, and CD8 T cells are also known as _______ T cells.

Answer 5

helper; cytotoxic

Question 6

Which organs are primary lymphoid organs?

Answer 6

bone marrow and thymus

Question 7

Which organs are secondary lymphoid organs?

Answer 7

lymph nodes and spleen

Question 8

Of the bone marrow and thymus, which is considered the CLP (common lymphoid progenitor)?

Answer 8

bone marrow

Question 9

What is the difference between Natural Killer Cells and CD8 (Cytotoxic) T-cells?

Answer 9

Cytotoxic T-cells are located in the adaptive immune system

Question 10

What does the HIV virus target and destroy in T-cells?

Answer 10

CD4

Question 11

Do immature T-cells have CD4 or CD8 glycoproteins?

Answer 11

Immature cells have BOTH

Question 12

Do mature T-cells have CD4 or CD8 glycoproteins?

Answer 12

Depending on the cell type, it will have one or the other.

(T-Helper: CD4, Cytotoxic T-cell: CD8)

Question 13

What are the phases of T-cell maturation/ selection?

Answer 13

• DN (double negative)
• DP (double positive)
• SP (single positive)

Question 14

What does CD stand for?
(In CD8 and CD4)

Answer 14

Cluster differentiation (proteins)

Question 15

What is the function of chemokines?

Answer 15

To attract mature B cells into the thymus

Question 16

What does “MHC” stand for in MHC I and MHC II?

Answer 16

Major Histocompatibility Complex

Question 17

When is the TCR beta chain first expressed?

Answer 17

At the DN (double negative), pre- T-cell stage

Question 18

What stage does the complete T cell occur? (has beta and alpha chains)

Answer 18

At the DP (double positive)

Question 19

When does a T cell become mature?

Answer 19

Once it has reached the single positive stage, either CD4+ or CD8+

Question 20

Failure of any cell to express/present _______ _______at any stage leads to ________.

Answer 20

antigen receptors (TCRs); apoptosis

Question 21

What functions as the checkpoints for recognizing self-antigens on the T cells?

Answer 21

MHC (Major Histocompatibility Complex)

Question 22

What is positive selection for T cells?

Answer 22

The T cell must recognize the MHC without too much recognition of the self-antigen it carries.

Question 23

When T cell receptors recognizes MHC I, the peptide complex loses expression of _______?

Answer 23

CD4

Question 24

When T cell receptors recognizes MHC II, the peptide complex loses expression of _______?

Answer 24

CD8

Question 25

Which MHC class does CD4 recognize?

Answer 25

MHC II

Question 26

Which MHC class does CD8 recognize?

Answer 26

MHC I

Question 27

What happens if a T cell does not recognize any MHC class?

Answer 27

apoptosis

Question 28

Why is it bad if a double positive (DP) T cell receptor strongly recognizes MHC?

Answer 28

Because the peptide complexes in the thymus will undergo apoptosis.

Question 29

What is the principle function of integrin?

Answer 29

adhesion

Question 30

What is the principle function of each: CD3, CD4/CD8, and CD28?

Answer 30

signal transduction

Question 31

What is the principle function of TCR?

Answer 31

specific recognition of an antigen

Question 32

Why do T cell progenitors have to pass 3 major checkpoints during development?

Answer 32

ensure they are MHC restrictive and non auto-reactive before forming CD4+ and CD8+ T cells

Question 33

What are the 3 checkpoints during T cell development?

Answer 33

(1) Beta selection (2) Positive selection (3) Negative selection

Question 34

What is the function of peripheral (secondary) lymphoid organs?

Answer 34

They provide an environment for the initiation of adaptive immune responses to foreign antigens.

Question 35

What happens during beta selection of the T cell?

Answer 35

Thymocytes undergo rearrangement of V/D/J gene of the beta chains. They are tested for successful rearrangement of the TCR beta.

Question 36

What stage does beta selection occur?

Answer 36

double negative (pre-T cell)

Question 37

What is the purpose of checkpoint #2 (positive selection)?

Answer 37

To see if the TCR alpha chain is able to function with the TCR beta chain. This is determined through the ability for the receptor to bind/recognize the self-peptide (MHC)

Question 38

What is the purpose of checkpoint #3 (negative selection)?

Answer 38

To determine the TCR safety through its ability to bind to self peptide-MHC on APCs with high affinity

Question 39

Is positive selection an antigen-dependent process?

Answer 39

Yes. If not, it repeats the rearrangement of the alpha chain until death by neglect.

Question 40

Why does a T-cell need both TCR alpha and TCR beta? (what do they bind to?)

Answer 40

TCR alpha binds to self-peptides while TCR beta binds to self-MHC

Question 41

What % of thymocytes successfully become CD4+ and CD8+ T cells?

Answer 41

~2%

Question 42

If the T-cell is antigen-dependent in the negative selection, what happens next?

Answer 42

clonal deletion

Question 43

What are Peyer's Patches?

Answer 43

gut associated lymphoid tissue (GALT)

Question 44

Where do B cells develop in dogs, pigs, and ruminants? Does it last for life?

Answer 44

Ileal Peyer's Patches in the intestines. Yes, lasts for life, but it shrinks in size. (ileum is the last part of the small intestine)

Question 45

What is the secondary lymphatic organ in the intestines and how long does it function?

Answer 45

Jejunum (2nd part of the small intestine); if lasts for life.

Question 46

What is the largest lymph node in the body?

Answer 46

spleen

Question 47

What are the T cell stages in order?

Answer 47

DN pro, DN pre, DP immature T cell, SP mature T Cell

Question 48

Which interleukin is essential for B cell maturation and growth?

Answer 48

IL 7

Question 49

What portions of BCR & TCR have the VDJ segments, and what portions of BCR & TCR have the VJ segments?

Answer 49

Heavy & Beta ; Alpha & Light

Question 50

Existence of BCR & TCR specificity for only one antigen is enabled by what?

Answer 50

Gene rearrangement of the variable region.

Question 51

At what T cell stage does VDJ recombination and RAG 1 & RAG 2 expression occur?

Answer 51

DN pro T cell stage

Question 52

At what T cell stage does the VDJ acts on the surrogate alpha chain?

Answer 52

DN pre T cell stage

Question 53

At what T cell stage is the alpha-chain tested on the established TCR-beta and auto-reactiveness is tested.

Answer 53

DP immature T cell stage

Question 54

At what T cell stage is CD4 w/ MHC 2 and CD8 w/ MHC 1?

Answer 54

SP mature T cell stage

Question 55

What causes proliferation of the DN pro T cell within the thymus?

Answer 55

IL 7 & thymic hormones

Question 56

Which hormone is secreted back to the T cell if it fails any of the checkpoints and tests?

Answer 56

Fas ligand (FasL) is a cell membrane cytokine that can trigger apoptosis. ## Footnote Razzle, dazzle, (FasL)

Question 57

What is the only way that a T cell can recognize an antigen?

Answer 57

It has to be presented by an MHC molecule

Question 58

What does heterodimer mean?

Answer 58

It is made of two chains

Question 59

What percent of T cells do alpha & beta chains present? gamma & delta?

Answer 59

alpha & beta - 95% of TCR gamma & delta - 5% of TCR

Question 60

What stage of T cell development do mature T-cells migrate to secondary lymphatic organs?

Answer 60

SP (single positive)

Question 60

What are the 3 types of T cells when mature?

Answer 60

CD4, CD8 and Regulatory T-cells

Question 60

Does the TCR have any special names like Ig M, Ig D, etc?

Answer 60

No

Question 61

Which chains for T cells contain VDJ genes?

Answer 61

beta and delta

Question 62

Which chains for T cells contain VJ genes?

Answer 62

alpha and gamma

Question 63

Give 2 examples of polypeptide hormones that act on the T cell in the DN stage and cause proliferation?

Answer 63

thymulin, thymic humoral factor