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Glossary of T Cell Activation

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Created by sammy1194

What is the TCR\'s basic function?
To sense what is going on the outside of the cell.

Name the two types of TCR\'s
Alpha/Beta & Gamma/Delta

How are TCR proteins assembled?
By mixing and matching gene segments.

The mixing and matching of gene segmentds, is similar to what other cell\'s mixing and matching of what?
Heavy and light chains of B Cells
In T & B cell what proteins initiate splicing of gene segments?
RAG1 & RAG2
What do RAG1 & 2 proteins do in T & B cells?
Initiate splicing of gene segments by making double stranded breaks in chromosomal DNA
What happens when RAG1 & 2 proteins create a double stranded break in chromosomal DNA in T & B cells?
It initiates gene segment splicing.
Can TCR\'s have both pair of proteins?
No
95% of T cells circulating the blood have gamma/delta TCR\'s
False, 95% of circulating T cells, TCR\'s are alpha/beta
95% of TCR\'s express what co receptors?
CD4 or CD8
What TCR don\'t express CD4 or CD8?
gamma/delta TCR
Where are T cells with gamma/delta TCR\'s most abundant in?
Intestine, uterus and tongue; which come in contact with the outside world.
Where are gamma/delta T cells found in mice?
Epidermal layer of the skin.
Are T cells found in the epidermal layer of the skin in humans?
No
Which pair of receptors are the least diverse?
Gamma/Delta
Where are gamma/delta T cells educated?
It\'s unknown
Where are alpha/beta T cells educated?
The thymus
What are gamma/delta T cells taught in the thymus?
They aren\'t taught at the thymus because it is not known where they are educated.
What are alpha/beta T cells taught in the thymus?
Not to react against our own self peptides.
What do gamma/delta T cells recognize?
It\'s unknown
What do some gamma/delta T cells do?
They kill cells that become stressed, due to a bacterial infection.
What does a TCR recognize outside of the cell?
MHC peptide complex

What classes of MHC molecules are there?
MHC1 & MHC2
How many MHC molecules does a t cell recognize?
only one
After a TCR recognizes its cognate antigen presented by an MHC molecule, what is the next step for the tcell
To transmit a signal from the surface of the tcell, to the nucleus.
What must happen in the nucleus for the tcell to be activated?
Gene expression must be altered
What does the external part of the transmembrane do?
It binds to a molecule called the ligand, outside the cell.
What does the internal part of the transmembrane do?
It initiates a biochemical cascade, that conveys a ligand bound signal to the nucleus
What is the ligand made out of?
MHC molecule and peptide
How long are the cytoplasmic tails of alpha/beta?
3 amino acids long
What proteins is CD3 made out of?
gamma,delta,epsilon & zeta
Where are the CD3 proteins located?
Anchored in the cell membrane.
How does a tcell get a strong signal to the nucleus?
clustering of receptors
What is recruited by the cytoplasmic tails of the CD3?
Kinase enzymes
Name all the proteins involved in the tcell,
alpha, beta, gamma, delta, epsilon, & zeta
What is the first step in t cell signaling?
All the proteins are transported to the surface of the cell
Alpha/Beta are great for?
Recognition
Alpha/Beta suck at?
Signaling
Gamma/Delta/Epsilon/Zeta are good at?
Signalig
Gamma/Delta/Epsilon/Zeta signal fine bur?
They are blind as to what is happening outside of the cell
During their education in the thymus, TCR are used to trigger?
Suicide by apoptosis
If the TCR recognizes MHC plus self peptides, what happens?
TCR trigger suicide(by apoptosis)
What happens if the TCR recognizes their cognate antigen presented by MHC molecule, but not the co-stimulatory signal?
The cell is anergized
What two things must happen in order for the T cell to activate?
It must recognize its cognate antigen and receive co-stimulatory signals
Killer T cells attach to what MHC molecule
MHC1
Helper T cell attach to what MHC molecule?
MHC2
Name 3 APCs
Dendritic cells, macrophage and B cells
Killer T cells express what co-receptor
CD8
Helper T cells express what co-receptor
CD4
What molecule does CD8 clip on to?
Class 1 MHC
What molecule does CD4 clip on to?
Class 2 MHC
Class 1 MHC clips on to?
CD8
Class 2 MHC clips on to?
CD4
What connects a MHC molecule to a TCR?
Peptides
What strengthens the adhesion between T cell and APC?
MHC molecules and CD4&8 co-receptors
CD4&8 function is to?
Focus the attention of Killer T cells and Helper t cells on the proper MHC molecule
CD4 is composed of how many proteins?
ONE
CD8 is composed of how many proteins?
TWO
How are CD4&8 glued to the tcell?
Loosely
When is the only time that the T cell expresses CD4 & 8 plus?
When it\'s maturing in the thymus
When the T cell is maturing in the thymus what does it express?
Both CD4 & 8 plus
How does the t cell decide which co receptor it will express?
unknown
What makes the signal from the membrane to the nucleus 100x stronger?
Co-stimulatory signal
T cells have a reduced requirement for co stimulation
True
Rafts on top of the t cell are made out of?
cholesterol
What do these \"rafts\" found on the top of t cells do?
They carry signals to the nucleus, when TCRs are engaged
What\'s the function of rafts in naive t cells?
None
When to TCRs and rafts come together?
When the TCRs engage with the cognate antigen
Where are rafts stored in naive tcells?
Inside the cell as other membranous parts
Why is it thought that the connection between TCRs and the nucleus isn\'t very strong in virgin tcells?
Lack of rafts
What is the other name of downstream signaling molecules?
rafts
When is it thought that the rafts are rushed to the surface?
when the tcrs engage to the cognate antigen and the application of co-stimulation
What is the job of rafts on top of mature tcells?
Carry signals
Name two co-stimulators of tcells
B7-1 & 2 proteins
Where are B7 proteins found?
On the surface of antigen presenting cells
How do B7 proteins provide co-stimulation?
By plugging into the receptors on the t cells surface
Name the two receptors that B7 proteins plug into on the tcell
CD28 & CTLA-4
When is CTLA-4 molecules expressed?
When the tcell has been activated

B7 proteins on APCs do what on virgin tcells?
Tie up the CD28 receptors, thereby providing a co-stimulatory signal for activation.
How do t cells turn off?









Ligation of CTLA-4 receptors by B7 proteins

T cells are part of what immune system?
Adaptive
Why is it important for the adaptive immune system to turn off?
So that B & T cells protect us against present and future invaders.

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