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CMB2004 > L05 > Flashcards

L05 Flashcards

1
Q

what do naive T cells do after exiting the thymus

A

recirculate via blood/lymphatics through secondary lymphoid tissue

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2
Q

what are the secondary lymphoid tissue

A

lymph nodes, spleen

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3
Q

what causes clonal proliferation and
differentiation of T cells

A

Contact with specific Ag and APC

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4
Q

what do naive T cells develop into

A

cytotoxic effector T cells (CD8+)- kill infected cells

helper effector T cells (CD4+) -secrete cytokines

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5
Q

what happens in the lymphoid tissue

A

T cells recognize Ag/MHC on antigen presenting cells (APC)

array of APC are found, some specialised, trap and present Ag
-lymph nodes
-spleen

Following activation, T cell ”effectors” leave these areas and migrate to sites of infection

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6
Q

how do T cells get to where they need to be?

A

enter lymph node from blood via high endothelial venules (HEV)

move into T cell area which is rich in dendritic cells and macrophages (APC)

APC present antigen and deliver other activation signals e.g. cytokines

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7
Q

what happens to T cells that are not activated (i.e. don’t see p/MHC)

A

they leave lymph node via cortical sinuses into the lymphatics; re-enter circulation

-> recycled for another day

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8
Q

how do T cells communicate

A

they express molecules on the surface (chemokine receptors)

bind ligands (chemokines) released by other cells

once close to other cells different molecular sets of CAMs mediate cell/cell interactions

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9
Q

list examples of cell/cell interactions through CAMs

A

naïve T cell with HEV

T cell with APC

effector T cell and target cell

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10
Q

what are the steps of T cell communications

A

1) T cells contact APCs using CAMs

2) TCR scans APC peptide/MHC complexes

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11
Q

what happens when a T cell does not recognize an Ag

A

it disengages

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12
Q

what happens when a T cell recognizes an Ag

A

starts a signal from TCR complex (CD3)

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13
Q

what does CD3 signal result in

A

increases affinity of CAM interactions

T cell divides

progeny differentiate to effector cells, exit LN
-> T cell-mediated response

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14
Q

how does the binding of TCR to the Ag affect LFA-1 and ICAM-1

A

T cells bind APC through low-affinity LFA-1:ICAM-1 interactions

subsequent binding of T cell receptors signals LFA-1

conformational change in LFA-1 increases affinity and prolongs cell-cell contant

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15
Q

how many signals do naive T cells need for activation

A

3

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16
Q

what is signal 1 in naive T cells

A

signal from TCR contacting MHC/peptide on APC involving CD3 (zeta) chain

17
Q

what is signal 2 in naive T cells

A

signal delivered by CD28 when it interacts with co stimulatory molecules (B7.1 and B7.2) expressed by APC

18
Q

what is signal 3 in naive T cells

A

cytokines (IL-6,IL-12, TGF-beta, IL4) bind cytokine receptors on naive T cells delivering the signal

19
Q

what does signal 1

A

activation

20
Q

what does signal 2 do

A

survival

21
Q

what does signal 3 do

A

differentiation

22
Q

what happens to a naive T cell after receiving the 3 signals

A

turns into an effector T cell

23
Q

does the effector T cell require the same levels and types of signals as the naive T cells to function

A

NO

it can function with lower co stim and cytokine

24
Q

what do activated T cells express

A

ICOS and CTLA-4

25
Q

what does ICOS do

A

binds ICOSL on APC to induce cytokines

26
Q

CTLA-4

A

is highly related to CD28, and shows stronger binding to B7.1/2 than CD28

27
Q

what does CTLA-4 do

A

antagonizes CD28 blocking signal 2

28
Q

what does the presence of non functioning CTLA-4 result in

A

autoimmune conditions

29
Q

how can anti CTLA-4 help in cancer treatment

A

can enhance the immune response to the tumour

30
Q

what happens when APCs encounter pathogens

A

APCs are activated and co stimulatory molecules are expressed

31
Q

what does APC activation lead to

A

APC upregulation of MHC and co-stimulatory molecules

32
Q

What are high endothelial venules

A

specialized vascular pathways into secondary lymphoid tissues from the blood

33
Q

List 3 types of cells that a T cell might interact with via a CAM

A

HEVs, APCs, and infected cells

34
Q

what does B7 on an APC bind to on a T cell

A

CD28 and CTLA-4

35
Q

what types of cytokines result in which type of T cells

A

IL-4 = TH2 cells

IL-12 and IFN-γ = TH1 cells

TGF-β and IL-6 = TH17 cells

IL-6 = TFH cells

TGF-β = Treg cells

36
Q

what is the function of dendritic cells in the secondary lymphoid organs

A

only present Ag to activate naive T cells

37
Q

what is the function of macrophages and B cells in the secondary lymphoid organs

A

present antigen in order to receive help from effector T cells

38
Q

hello

A

hi

39
Q
A

CMB2004 (12 decks)

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