MI 03b: T Cell Activation Flashcards by Nuna H

Goals of T cell activation: to generate (X) and (Y).

X = large number of effector cells
Y = antigen-specific memory T cells

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What defines a “naive” T cell?

Hasn’t encountered antigen yet (recirculating)

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Epithelial barrier is breached. Microbes and their products are taken up by (X), which process the protein components into (Y) for MHC presentation.

X = dendritic cells
Y = peptides

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As DCs process antigen, they migrate from (X) to (Y).

X = infected tissue
Y = T cell zones (draining lymph nodes)

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T/F: During migration to T cell zone, DCs upregulate expression of MHC and co-stimulatory molecules.

True

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T/F: Upon activation, T cell leaves the lymph node right away.

False - stays in lymph node for few days

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T cell activated. Which subsequent processes occur prior to it leaving lymph node?

Receptors and signaling pathways activated
Surface molecules change
Cytokines produced
Clonal expansion

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The cytokine (X) is particularly important in T cell proliferation.

X = IL-2

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T cell activation: Signals from different (X) enable differentiation of CD4 T cells to (Y) or CD8 T cellsto (Z).

X = cytokines;
Y = helper T cells
Y = cytotoxic T cells

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In normal, healthy T cell response, expansion and decline of responses occurs over (X) period of time.

X = 1-2 weeks

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Blood-borne pathogens are captured by (X) cells, primarily in (Y) location.

X = APCs 
Y = spleen

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T/F: DCs are the best APCs.

True

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What are the classes of DCs?

Classical

2. Plasmacytoid

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(X) class of DCs is the primary source of (Y), which are crucial for anti-viral immune response.

X = plasmacytoid
Y = Type I IFN

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Which class of DCs primarily responsible for presenting antigen to naive T cells?

Classical

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Unstimulated DCs typically reside in:

Epithelial and sub-epithelial tissue layers

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What do bored, unstimulated DCs typically do in their spare time?

Very mobile and phagocytic (constantly sample environment for microbes)

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T/F: DCs themselves may be infected by viruses.

True

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It’s typically (X) binding to (Y) of DCs that begin their maturation process.

X = PAMPs
Y = PRRs (i.e. TLRs)

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As DCs take the trip to T cell zones, which of their molecules are (up/down)-regulated?

Up-regulate:

MHC
B7 co-stim
ICAM-1 (integrin ligand)
CCR7 (chemokine receptor)

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Which integrin (receptor/ligand) is up-regulated on migrating DCs?

Ligand;

ICAM-1

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Maturing DCs know the path to T cell zone because they (gain/lose) (X) and (gain/lose) (Y).

Lose;
X = adhesiveness to epithelial cells
Gain;
Y = expression of CCR7 chemokine receptor

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Migrating DCs express (X) receptor, which directs them toward (Y) via chemotaxis. The chemokines are produced by (Z).

X = CCR7
Y = Z = lymph nodes

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(One/hundreds) of naive T cells will interact with (one/hundreds) of DCs in any given day.

One; hundreds

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Which signals are necessary for T cell activation?

1. Antigen recognition | 2. Co-stimulation

T/F: TCR is a signaling molecule.

False

T/F: TCR is non-covalently associated with signaling molecules.

True

TCR of naive T cell binds complementary peptide-MHC complex. Signal transduction occurs via which molecule(s)?

CD3 and zeta chains

T/F: Signal 2 of T cell activation involves CD4/CD8 co-receptors.

False - they're involved in signal 1

(X) co-receptors on T cells increase binding (affinity/avidity) between TCR and APC. This is involved in Signal (1/2) of T activation.

X = CD4 or CD8 Avidity; Signal 1

Signal 2 of T activation provided by binding of (X) to (Y).

``` X = CD28 on T cell Y = B7 on DC ```

There's (positive/negative) feedback in Signal (1/2) of T activation. Describe this.

Positive; Signal 2; T cells further up-regulate CD28 expression upon receiving co-stimulatory signal from DCs

In general, T activation signals 1 and 2 work together. Signal 1 provides (X). Signal 2 provides (Y).

``` X = specificity Y = protection against autoimmunity ```

T cell activation: T cell contains integrin (receptor/ligand) (X) that binds to (Y) on APC.

Integrin receptor X = LFA-1; Y = integrin ligand (ICAM-1)

It's important to avoid (over/under)-production of (X) cytokine, a potent T-cell growth factor. How is this done?

Over-production; X = IL-2; Its mRNA is inherently unstable

Signaling from T cell activation causes which events to occur, in terms of IL-2 production?

Increased IL-2 production via: 1. Stabilization of mRNA 2. Up-regulate transcription factors

Activated T cells have (more/less) (receptors/affinity) for IL-2.

More receptors and increased affinity

IL-2 in T cell activation has (autocrine/endocrine/paracrine) actions.

Autocrine (same cell) and paracrine (nearby T cell)

Which region(s) of which cell(s) constitute the immunological synapse?

Contact region between T cell and APC

Within immunological synapse (on T cell), (X) receptors/molecules cluster and (Y) are pushed to periphery.

``` X = TCR, co-receptors, and CD28 Y = LFA-1 ```

Lck is a(n) (X) that's associated with (Y) in/on (surface/cytosol) of (Z) cell.

X = tyrosine kinase; Y = CD4 or CD8 co-receptors Cytosol; Z = T cell

Lck action.

Phosophorylation of ITAMs on CD3 and zeta chains

ITAMs are (X)-based activation motifs found on (Y) in (Z) cell.

``` X = Tyrosine; Y = CD3 and zeta chains Z = T cell ```

(Dephosphorylated/phosphorylated) ITAMs stimulate signaling along which pathways?

Phosphorylated; 1. PLC(gamma) 2. Ras/Rac 3. PI3 kinase

T cell signaling pathways final generated products.

Transcription factors (NFAT, NFkB, AP-1)

T cell signaling pathways are important targets for (X) drugs.

X = immunosuppressive

(X) cells are unique in having the capacity to bypass rules of antigen presentation via cross-presentation. Explain.

X = dendritic Microbe phagocytosed (MHC II loading) and, during processing, some antigen spills into cytosol (now also available for MHC I loading)

There's a safeguard in place for differentiation of CD(4/8) T cells into cytotoxic T cells. What's the safeguard?

CD8; | CD4 T cells must be co-activated (produce cytokines that aid differentiation)

Some pathogens secrete (X), which induce unspecific activation of many CD(4/8) T cells and massive release of (Y).

X = super-antigens; CD4; Y = cytokines

List the subsets of T helper cells that CD(4/8) T cells can differentiate into.

CD4; Th1, Th2, Th17, Tfh

Difference between Th1, Th2, and Th17 cells is essentially which (X) they (Y).

``` X = type of pathogen Y = are programmed to fight ```

Tfh, aka (X), cell has key role of:

X = follicular helper T cell assisting B cells with Ab production

T/F: The T helper (effector) cells don't exit peripheral lymphoid organs.

False - only Tfh doesn't exit

List the general types of receptors expressed on T cells that allow for their migration/trafficking.

1. Chemoattractant receptors 2. Selectins 3. Integrins

Naive T cells express which receptor(s) to direct their trafficking to (X)?

1. CCR7 2. L-selectin 3. LFA-1 (integrin) X = T cell zone

Naive T cells migrate from (X) into (Y) through (Z) structures.

``` X = blood circulation Y = lymph node T cell zone Z = high endothelial venules (HEVs) ```

(X) are specialized endothelial cells that facilitate (slowing/speeding) of T cells through which interactions?

X = HEVs; Slowing; 1. L-selectins 2. Integrins (ICAM-1 and LFA-1)

L-selectin (ligand/receptor) on naive T cell interacts with (X) (ligand/receptor) on (Y) during migration.

Receptor; X = L-selectin Ligand; Y = HEVs

Integrin (ligand/receptor) (X) on naive T cell interacts with integrin (ligand/receptor) (Y) on (Z) during migration.

``` Receptor; X = LFA-1; Ligand; Y = ICAM-1; HEV ```

Activated effector T cells, unlike naive T cells, are not drawn into (X) due to lack of expression of (Y) (receptor/ligand).

X = peripheral lymph organs; Receptors Y = CCR7 and L-selectin

To exit lymph nodes, (activated/unactivated) T cells up-regulate expression of (X). This will help them leave because (Y) is (higher/lower/absent) in blood.

Unactivated (circulating); X = Sphingosine-1-P (S1P) receptor; Y = S1P; Higher

If T cell activated in lymph node, its exit is (facilitated/supressed) by (activation/suppression) of (X).

Supressed; Supression X = S1P receptor levels

MI 03b: T Cell Activation Flashcards

(62 cards)