T Cell Mat/act/diff

Front 1

4 things that happen in the Thymus:

Back 1

1. Progenitor Tcells proliferate (before having any surface markers)

2. DNA gene rearrangement

3. T cell selection

4. Differentiation of mature T cells into distinct subpopulations

Front 2

Steps in Differentiation of a Progenitor T cell:

Back 2

1. Progenitor undergoes 1st DNA rearrangement -> 2 types of doub neg cells (a/b TCR, y/d TCR (minor)).
2. Gene rrngmt -> Doub POS cells.
3. Double selection (pos and neg)
4. diff into SINGLE POS, CD3+, MATURE T cells.

Front 3

What are the two things that happen in Thymic selection?

Back 3

-Positive selection
-negative selection

Front 4

What is positive selection?

Where does it happen?

Back 4

Selection of only the T cells that bind self-MHC.


Occurs in the Thymus cortex.

Front 5

What is negative selection?

Where?

Back 5

Selection of only the T cells that bind self-molecules appropriately - if too tight, they undergo apoptosis.


Occurs in medulla

Front 6

How do Doub pos T cells differentiate into Single pos -> CD4+ versus CD8+?

Back 6

-Instruction model

Those cells that interact with MHC1 become CD8;

Those cells that interact with MHC2 become CD4.

Front 7

What is triggered by the initial formation of the trimolecular complex (TCR+Ag/MHC, and coreceptors binding)?

Back 7

TRANSMEMBRANE SIGNAL CASCADE.

Front 8

what are the components of the signal cascade?

Back 8

-Tyrosine Kinase
-PKc
-Ca2+ calcium ions
-Small g proteins

Front 9

What is the consequnce of the signal transduction cascade?

Back 9

induces the transcription/translation of activation factors like cytokines, cell-adhesion molecules, etc.

Front 10

How many signals does Tcell activation require?
What are they?

Back 10

2.

1. Antigen binding (signal transduction)
2. Co-stimulatory signal (B7/CD28)

Front 11

What three gene products does Signal 1 turn on, in what order?

Back 11

1. Transcription factors

2. Cytokine/cytokine receptors

3. Adhesion molecules

In That Order

Front 12

What REALLY activates the transduction signal cascade, on CD3?

Back 12

ITAMs -> CD4 binds to MHC and makes Tyrosine kinases bind and phosphorylate ITAM motifs on CD3. triggers signaling cascade that activates the tcell

Front 13

What is the Co-stimulatory signal?

What does it immediately cause?

Back 13

A non-antigen-specific binding of CD28 on Tcells with B7 on APCs.


Immediately Tcell turns on CTLA-4; competes with its own CD28 to prevent over-activation.

Front 14

What does the co-stim signal do to the APC themselves?

Back 14

Upregulates B7 to enhance activation of more tcells

Front 15

Tcells bind APC, but no co-stimulatory signal is available; what happens?

Back 15

The tcell will go into Anergy - nonresponsiveness, no cytokines produced, no proliferation.

Front 16

Tcell binds APC, and receives co-stim signal; what happens?

Back 16

Tcell will proliferate into clones.

Front 17

What type of mature T cells are produced from the maturation and selection in the thymus?

Where do they go?

Back 17

mature Naieve tcells.


Go to peripheral lymphoid tissue to search for their antigens.

Front 18

What happens when a mature naieve Thelper cell encounters its antigen?

Back 18

-Activation makes it produce IL-2 and IL2-receptor.

-Proliferation and differentiation into Th1 and Th2 subsets.

Front 19

what are the 2 subpopulations of Thelper cells, and what's the main difference?

Back 19

Th1 subpopulations -> activate Tc cells and macrophages.

Th2 subpopulation -> activates Humoral Bcells.

Difference: which cytokines they secrete.

Front 20

What are the PROFESSIONAL Ag-presenting cells?

Back 20

Dendritic cells

Front 21

What's the difference between PROFESSIONAL (dendritic) APC versus Macrophages or Bcells?

Back 21

Dendritic have constitutive B7, MHC2, and activate every kind of Tcell.


Macrophages only have induced B7, MHC2, and do not activate naieve Tcells.

Bcells have induced b7 and have to be activated to activate naive Tcells.

Front 22

What 2 factors can trigger Apoptosis?

Back 22

-Tcr stimulation (without costim signal)


-Glucocorticoid treatments

Front 23

What receptor/ligand interaction triggers Apoptosis?

Back 23

Fas and Fas ligand

Front 24

What do superantigens do?

Back 24

Crosslink TcR and MHC nonspecifically and tightly, causing overactivation of Cytokine production.

Front 25

What are consequences of Superantigen?

Back 25

Toxic shock
Tcell population wipe-out

Front 26

Where are yd Tcells mainly, what is the function?

Back 26

in epithelial cells of skin.


remove dad cells and protect the skin from pathogens.