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Immunology > Lecture 11: Activation of T Lymphocytes > Flashcards

Lecture 11: Activation of T Lymphocytes Flashcards

1
Q

Ag recognition by T cells induces what

A

Secretion of IL-2 which causes T cell proliferation

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2
Q

Three signals required for proliferation and differentiation of T lymphocytes into memory cells

A

Ag recognition (signal 1)
Costimulation (signal 2)
Cytokines (signal 3)

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3
Q

Activation of naïve T cells requires

A

Presentation of Ag by dendritic cell

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4
Q

CD28:CTLA4 complex on T cells is

A

Inhibitory signal

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5
Q

CD28:CD80/86 complex on T cell is

A

Activating signal

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6
Q

CD2:CD48/59 complex on T cell is

A

Adhesion with APCs

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7
Q

LFA1:ICAM1 complex on T cell is

A

Adhesion with APCs

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8
Q

Ag recognition without costimulation may cause

A

Formation of anergic or unresponsive T cells

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9
Q

Costimulatory molecule expression on unactivated DCs

A

Low levels of costimulatory molecules, not enough to activate naïve T cells

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10
Q

What stimulates the differentiation of naïve T c ells into effector cells, and it is released by what

A

IL-12 released by activated DCs

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11
Q

APCs express ___ while T cells express ____ (in the context of B7/CD28 complexes)

A

APCs express ligands while T cells express receptors

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12
Q

CTLA4 mediated immune checkpoint

A

Induced in Naïve T cells at the time of their initial response to Ag

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13
Q

Naïve and memory T cells express high levels of ____ but do not express ___

A

Naïve/memory T cells express high levels of CD28 but do not express CTLA4 which is stored in intracellular vesicles

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14
Q

When is CTLA4 expressed

A

After the TCR is triggered by Ag encounter- the stronger the stimulation, the greater the amount of CTLA4

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15
Q

CTLA4 functions as a

A

Signal dampener to maintain a consistent level of T cell activation

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16
Q

Major role of PD1

A

Not at the initial T cell activation stage

  • Regulates inflammatory responses in tissues by effector T cells recognizing Ag in peripheral tissues
  • Activated T cells upregulate PD1 and express it in tissues
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17
Q

PD1 ligand expression is induced by

A

Inflammatory signals in the tissues

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18
Q

PD1 Ligand function

A

Downregulate the activity of T cells and thus limit collateral damage in response to infection

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19
Q

What is the best characterized signal for PD1L induction

A

IFN-y released by Th1 cells

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20
Q

Excessive induction of PD1 on T cells (in setting of chronic Ag exposure) can induce

A

An exhausted or anergic state in T cells

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21
Q

Quick steps in generation of Th1 cells

A

IL-12 activates STAT4 which leads to expression of T-bet which facilitates generation of Th1 cells

22
Q

Quick steps in generation of Th2 cells

A

IL-4 activates STAT6 that leads to expression of GATA-3 which facilitates generation of Th2 cells

23
Q

Quick steps in generation of Treg cells

A

TGF-b activates SMAD2-SMAD4 which promotes the expression of FOXP3 and the generation of T regulatory cells

24
Q

SAgs

A

Most powerful T cell mitogens ever discovered
Not processed into peptides
Simultaneously bind MHC II molecules (not in peptide binding groove) and the V region of the B-subunit of the TCR

25
SAgs induce
A robust proliferation of SAgs-activated T cells which produce massive amounts of pro-inflammatory cytokines TNF, IL-1 and IL-2 which may lead to shock
26
IL-2 costimulates T cells to produce
IL-4, IL-5 and IFN-y
27
How does IL-2 help reduce apoptosis and stimulate the cell cycle
Induces anti-apoptotic protein Bcl-2 | Stimulates cell cycle progression by degradation of cell cycle inhibitor p27
28
IL-2 is required for the ____ and ____ of ____
Survival and function of Treg cells
29
Function of newly expressed CD69 on activated T cell
Retention in lymph node
30
Function of newly expressed IL-2R on activated T cell
Proliferation
31
Function of newly expressed CD40L on activated T cell
Activation of APCs
32
Function of newly expressed CTLA-4 on activated T cell
Control of response
33
CD69 function explained
CD69 associated and inhibits the function of S1P(1), inhibiting egress from LNs CD69 binding reduces surface expression of S1PR1
34
Result of CD69 binding to activated T cell
T cell is retained in the LN long enough to receive signals that initiate proliferation and differentiation CD69 expression decreases after cell division
35
Blood and lymph S1P extracellular concentration vs lymphoid organ S1P extracellular concentration
Blood/lymph S1P concentration is high, which causes down regulation of S1PR1. When it enters the lymph organ with low [S1P], it begins to re-express higher levels of S1PR1
36
CD40L expression is induced by
Ag recognition by T cell. Takes 24-48 hours
37
CD40:CD40L complex between T-cell/APC may stimulate
The expression of more B7 (CD28) molecules and the secretion of cytokines that activate T cells
38
As the level of costimulation and IL-2 decrease, what else decreases
The levels of anti-apoptotic proteins in the cell
39
What triggers the mitochondrial intrinsic pathway of apoptosis with respect to the decline of T cell responses
IL-2 starvation
40
What cells constitute the most abundant lymphocyte population in the body during lifetime
Memory T cells
41
Linear model of memory T cell differentiation
Most effector cells die, some survivors develop into memory cells
42
Majority of memory T cells reside where
In tissue sites- lymphoid tissues, intestines, lungs, skin
43
T-bet function in effector T cells
Drives differentiation of effector cells in CD4+ cells
44
Blimp-1 function
Promotes the generation of memory cells
45
Resident memory T cells (Trm)
Produce IFN-y and TNF and are specific for pathogens/Ags that have been encountered previously
46
Central memory T cells (Tcm)
Express chemockine CCR7 and L-selectin and home to LNs, spleen and circulate in blood
47
Effector memory T cells (Tem)
Circulate in the blood Do not proliferate, but produce IFN-y and TNF or become cytotoxic Upon entering tissue, Tem cells can become Trm cells and reside in epithelial barrier tissues
48
How do memory cells survive in quiescent state without Ag
They express increased levels of anti-apoptotic proteins
49
Memory T cell response compared to naïve T cell
Larger, faster, enhanced responses Naïve cells take 5-7 days, memory cells take 1-3 days There are more memory cells specific for a particular antigen than there are naïve cells
50
Maintenance of memory cells is dependent upon
Cytokines, but does not require Ag presence
51
What cytokines induce expression of anti-apoptotic proteins and stimulate low level proliferation
IL-7 and IL-15
52
Quick steps in generation of Th17 cells
IL-6 activates STAT3 the leads to expression of RORyt which facilitates generation of Th17 cells

Immunology (21 decks)

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