T Cells-Development

Question 1

What are thymocytes?

Answer 1

developing T cells within the thymus

Question 2

gamma delta T cells

Answer 2

• maintain tissue integrity
• do not express CD4 or CD8 or CD4 co-receptors
• interact with non-classical receptors

Question 3

CD4 T cells

“top of pyramid of immune cells

Answer 3

• helper T cells
• several subtypes
• Regulate adaptive and innate immune function
• MHC II

Question 4

CD8 T cells

Answer 4

cytotoxic T cells
direct effector function
interact with
MHC I

Question 5

Thymus structure

Answer 5

• site of all T cell development
• TCR development within the cortex
• selection as thymocytes move from cortex to medulla

Question 6

The thymus involutes with Age

Answer 6

reduced T cell production
T cells have long half lives
-CD4 4.2 yrs
-CD8 6.5 yrs
T cell-mediated immunity is not grossly affected

Question 7

T cell progenitors don’t commit until they reach the thymus why?

Answer 7

Notch 1 binds to receptors on thymic epithelium and is cleaved.
-activates transcription factors and produce IL-7

Question 8

Why is Notch-1 important

Answer 8

T cells determine that they are in the right spot by Notch signaling, and this induces responsivity to IL-7

Question 9

what are the three phases of T cell development?

Answer 9

double-negative
double-positive
single-positive

Question 10

what occurs in the double negative T cell

Answer 10

the beta chain rearranges to form a functional pre-TCR and this is the first check point

Question 11

what occurs in the double positive T cell?

Answer 11

the CD8 and CD4 are expressed while the alpha chain is rearranging and then you get a functional TCR.
-Positive and negative selection occurs as the second check point

Question 12

what occurs in the single positive T cell

Answer 12

after the T cell passes the positive and negative selection the T cell is then selected to either be CD4 or CD8, but not both

Question 13

what can occur during both double negative and double positive phases?

Answer 13

the T cell cell become gamma:delta

Question 14

if you are going to become and alpha beta T cell what rearranges first?

Answer 14

the Beta chain

Question 15

If gamma or delta rearrange first what happens?

Answer 15

the Beta and alpha are suppressed

Question 16

Beta-chain production drives the production of what?

Answer 16

CD4 and CD8 expression to make a double positive T cell

Question 17

After Beta-chain rearranges what happens?

Answer 17

the alpha chain rearranges to form a functional TCR

Question 18

what can happen during alpha chain rearrangement?

Answer 18

gamma:delta can rearrange and shift to a gamma:delta T cell

Question 19

Does the alpha or beta chain form the pre-T cell receptor?

Answer 19

beta

Question 20

why do are most all T cells alpha beta and not gamma delta?

Answer 20

because the gamma and delta have the rearrange before the one beta chain

Question 21

how many attempts does the beta chain get to rearrange?

Answer 21

4

2 per loci and there are 2 genes

Question 22

the beta chain is equivalent to what of the immunoglobulin?

Answer 22

the heavy chain in terms of rearrangement

Question 23

what is the order of rearrangement of the beta chain?

Answer 23

1st: D+J=DJ
2nd: DJ+V=DJV

Question 24

T/F the Beta chain locus is organized differently than immunoglobulin chains?

Answer 24

true

Question 25

what is the first checkpiont of T cell development?

Answer 25

the pre-T cell receptor

Question 26

What are the components of Pre-T cell receptors?

Answer 26

beta chain with a surrogate alpha chain analogue

Question 27

what assembles after the beta chain and the surrogate alpha chain bind as a superdimer?

Answer 27

the CD3 complex

Question 28

why is the CD3 complex important?

Answer 28

- drives proliferation - RAG function halts - also drives of expression of CD4 and CD*

Question 29

once T cells become double positive what happens?

Answer 29

the alpha chain rearranges

Question 30

why can a gamma: delta T cell still occur during alpha rearrangement?

Answer 30

because the delta locus is within the alpha locus | *once alpha rearranges, gamma:delta can no longer occur

Question 31

what are the components of the alpha chain that rearrange?

Answer 31

the V and J just like the light chain of immunoglobulins

Question 32

once the alpha chain has rearrange what is expressed on the surface of T cells?

Answer 32

functional TCR and CD4 and CD8

Question 33

what is positive selection of T cells

Answer 33

checks for functional TCR

Question 34

what is negative selection of T cells?

Answer 34

no self-antigen binding

Question 35

positive selection ensures what?

Answer 35

MHC is bound by co-receptor (CD4 and CD8) - alpha chain rearrangement can occur - binding turns off RAG 1/2 complex * *second check point

Question 36

Positive selection: determines CD4 or CD8 expression how?

Answer 36

``` it just depends which MHC class it binds, so if it binds MHC I first then it becomes a CD8, the opposite is also true for MHC II and becoming CD4 -binding of a particular MHC will down regulate the other CD receptor type ```

Question 37

negative selection: prevents self-antigen binding. How?

Answer 37

dendritic cells and macs present self peptides - excessively binding induces apoptosis - prevents autoreactivity - central tolerance - peripheral tolerance may also occur

Question 38

once a T cell has passed positive and negative selection, what are they considered?

Answer 38

mature naive T cells | - meaning the have not bound antigen or been activated yet

Question 39

what happens to the mature naive T cell?

Answer 39

it is released into blood steam and enters the lymph nodes for days and the move through the lymphatic system to look for antigen.

Question 40

what are the Two major stages of T cell development?

Answer 40

double negative and double positive

Question 41

what is the process of T cell receptor?

Answer 41

- beta rearranges to form pre-TCR and forms superdimer to express CD3 which expressed CD4 and CD8 as well as proliferation and RAG function halts. - alpha chain rearranges and a functional TCR and CD4 and CD8 and are called double positive