What do these "primary" signals entail for a T-cell to be activated? 1. T Cell Receptor 2. Co-Receptor 3. Co-stimulation

1. TCR must recognize its cognate antigen 2. co-receptor must recognize the MC (I or II) 3. other receptor(s) must recognize other molecules

Exam 1-- Ch.5 T Cells Flashcards by Michelle Farrow

What are T cells? Where are they produced? Where do they mature?

WBCs from bone marrow that mature in the thymus

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Where are T cells found? How many?

circulate in blood and lymph (can enter tissue)

–billions!

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What type of receptors to T-cells have? What do they recognize?

T Cell Receptors (TCRs)
- “antibody like receptors” (are NOT Ab, like how B-cells have)

recognize protein antigens presented by MHCs

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What are the two types of T cells?

Killer T cells (aka Cytotoxic T Cells – CTLs)

Helper T cells

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What activates Killer T cells (CTLs)?

by MHC I and abnormal peptide presented on cells

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T/F. Very few cells in body can present antigen to CTLs (T Killer Cell) via MHC class I molecules.

False– most cells can

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What occurs after the Killer Cell connects to the target cell?

triggers apoptosis, for it to commit suicide

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What activated Helper T cells?

MHC II and abnormal Antigen Presenting Cells (B-cells, macrophages, or dendritic cells)

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What will a T Helper Cell do after it is activated?

secrete cytokines

interleukin 2 (IL-2)
interferon gamma (IFN-gamma)

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Recall: Which cells are presenting MHC I? What about MHC II? What does the peptide look like they are presenting? What T cell are they stimulating?

MHC I – infected cell presenting endogenous; peptide enclosed; T Killer Cell

MHC II – APC; peptide sticks out; T Helper Cell

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What are the three “primary” signals a T cell needs to be activated?

T Cell Receptor
Co-Receptor
Co-stimulation

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What do these “primary” signals entail for a T-cell to be activated?

T Cell Receptor
Co-Receptor
Co-stimulation

TCR must recognize its cognate antigen
co-receptor must recognize the MC (I or II)
other receptor(s) must recognize other molecules

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What is the difference b/w a Co-Receptor and Co-Stimulation?

Co-receptor is recognizing the MHC (I or II)

Co-stimulation means recognizing other molecules

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What occurs if the T cell’s TCR recognizes MHC plus self peptides?

the T-cell commits suicide (apoptosis)

– (T cells created that would kill self need to go away)

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What occurs if the T-cell’s TCR recognizes cognate antigen(non-self) on MHC with no co-stimulation?

T cell is anergized (inactivated)

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What occurs if the T-cell’s TCR recognizes cognate antigen on MHC plus there is co-stimulation?

T cell is activated

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T/F All T-cell TCRs only recognize peptides presented by MHC I and MHC II molecules.

True

What are the two types of TCRs?

alpha-beta (95%) –traditional

2. gamma-delta –non-traditional

T/F. All TCrs on a given mature T cell are usually different.

False– they are usually ALL identical!!!

What is the name given to the group of signaling proteins ass. with TCR?

CD3

What are the elements needed for a T-cell to be activated?

Recognition (TCR–alpha-beta; and Co-receptor–CD4 or CD8)
Co-stimulation (B7 on APC; and CD28 on T-cell)
Signaling (CD3; and CD28 on T-cell)

What is the TCR proteins (alpha-beta) needed for?

antigen recognition

What is the co-receptor needed for?

the co-receptor = CD4 or CD8–(on T-cell); are for MHC recognition

What are the co-stimulatory molecules?

B7 proteins on APC

What is CD3 needed for?

signaling | or those other 4 proteins-- weird symbols

What type of T-cell expresses CD4? What MHC is then involved? What type of signal is created?

Helper T cells; attaches TCR to MHC II molecules HELP signal

What type of T-cell expresses CD8? What MHC is involved? What type of signal is created

Killer T Cells (CTLs); attaches TCR to MHC I molecules KILL signal

What are the two kinds of Co-receptors of T-cells?

CD8 ---> is MHC I restricted (peptides in cell) CD4--> implies MHC II (peptides from outside cell)

What do the co-receptors do for T-cells? Why are they important?

Co-receptors bind T cells to MHCs (Type I or II) w/o them the T-cell would not know if an APC is presenting protein fragments and need help (helper T) or if an APC is infected and needs to be killed (killer T)

What can created the Co-stimulation of T-cells?

many moelcules! | - B7 proteins (CD80, CD86) from APC's, connect with CD28 receptor on T-cell

What is B7? What is CD28? What occurs when CD28 is activated?

B7--> is a co-stimulatory molecule expressed on surface of APCs CD28--> is a receptor molecule on T-cell; when activated it amplifies signal and lowers number of TCR crosslinks needed for activation

What are Helper T cells constantly doing in the lymph nodes?

scanning dendritic cells; if find cognate antigen it will: - TCR engages antigen/MHC - CD4 co-receptor on Helper T cell attaches to MHC II on dendritic cell - CD40L proteins attach to CD40 on dendritic cell - dendritic cell makes co-stimulatory molecules (B7) - adhesion molecules bind two cell together (immunological synpase)

Once the Helper T cells are fully activated and bound to the dendritic cells, what happens next?

Helper T cell and APC part ways - Helper T proliferates and makes more IL-2 - APCs goes on to activate other Helper T cells

What does IL-2 serve as for Helper T cells?

a positive feedback for division

Do naive T cells have IL-2 receptors on their surface? What does this results in?

No, therefore only T cells replicating are specific ones needed to combat the particular antigen

How are Killer T cells activated?

only need an activated dendritic cell for activation

What is the process of a Killer T cell becoming activated?

- Naive CTL meets activated DC presenting cognate antigen on a MHC I - Co-receptors and co-stimulation occur (CD8 on Killer T cells binds to MHC I) (same concept as helper T cells)

How long to dendritic cells and Helper T cells bind for? What occurs during this time?

for hours | - emit cytokines which attract CTLs

Which cell is in charge of supplying IL-2 for CTL proliferation? What cell regulates magnitude of CTL response?

Helper T cells!!

What are non-traditional T cells?

- T cells that express gamma-delta receptors - are Natural Killer T cells (somewhat b/w T cells and NK cells) - have traditional alpha-beta receptors

Where are Non-Traditional T cells most abundant?

- intestine - uterus - tongue

What do non-Traditional T cells recognize?

lipid antigens presented by non-traditional MHC- called CD1