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YEAR 2 S2 IMMUNO > Theme 4 - 4b (T cell activation pt 2 and T cell effector functions) > Flashcards

Theme 4 - 4b (T cell activation pt 2 and T cell effector functions) Flashcards

1
Q

what determines what specifc T helper cell a T cell will becomes

A

cytokines produced by APCs

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2
Q

what generally do T helper 1 cells do

A

mediate cell mediated immunity

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3
Q

what generally do T helper 2 cells do

A

mediate humoral immunity

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4
Q

what effect does signal 3 (polarising factors) have on the T cell

A
  • induces TF activation

- causes T cells to produce different things eg T H 1 cells prod INTERFERON GAMMA and T H 2 produces IL4,5.13

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5
Q

how does CROSSREGULATION occur

A
  • activation of ONE TF and thus development of TH1/TH2 cells will INHIBIT the development of th eother type of immune response
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6
Q

what is the master regulatory TF for TH1 cells?

A

T-Bet (activation of T-Bet inhibits activation of GATA-3)

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7
Q

what is the master regulatory TF for TH1 cells?

A

GATA-3 (activation of GATA-3 inhibits activation of T-Bet)

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8
Q

is the T H subset fixed

A

no, it can change as the immune response develops

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9
Q

do CD8+ T cells need MORE or less stimulation than TH cells to be activated

A

MORE (as they are cytotoxic)

  • this is provided by CD4+ T helper cells (Th1 or Th17) that have recognised antigen on the APC
  • the activation from CYTOKINES (IL-2) released from CD4+ T cells
  • CD4+ T cells also ACTIVATE DCs via C40 TO CD40 ligand activation, this makes the DC BETTER at activating the CD8 T cell
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10
Q

what is the effect of CD40

A
  • CD40L binds to CD40 on the APC, which stimulates it to make more co-stimulatory CD80/CD86 O ENHANCING activation of the CD8 T cell
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11
Q

in CD8+ T cell activation, what causes activation of CD4 T cells

A

the dendritic cell activates both CD8+ and CD4+

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12
Q

T cells must be activated by what

A
  • by RELATED ANTIGENS presented by BOTH MHCI and MHCII on the SAME APC
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13
Q

what % of MHC class I molecules present peptides from EXOGENOUS antigens

A

25%, this is a process that isnt understood well

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14
Q

what is cross presentation

what is it important for

A

the presentation of EXOGENOUS antigens on MHC class I by unknown mechanism

  • paramount for the activation of CD8+ T cells
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15
Q

what is cross presentation

what is it important for

A

the presentation of EXOGENOUS antigens on MHC class I by unknown mechanism

  • paramount for the activation of CD8+ T cells
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16
Q

TH1 cells are involved in what type of mmune response

A

cell mediated immune responses (fighting INTRACELLULAR pathogens eg things taken up by macrophages or viruses in cells)

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17
Q

TH1 cells can interact with macrophages using WHAT LIGAND

where does this occur

A

CD40 LIGAND (CD40 L ) on T cell interacts with CD40 on APC induces macrohphage to be BETTER AT KILLING the microbe it has phagocytosed

  • occurs in the PERIPHERAL tissue, where the infection actually is
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18
Q

TH1 cells can interact with macrophages using WHAT LIGAND

where does this occur

A

CD40 LIGAND (CD40 L ) on T cell interacts with CD40 on APC induces macrophage to be BETTER AT KILLING the microbe it has phagocytosed

  • occurs in the PERIPHERAL tissue, where the infection actually is
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19
Q

what is the effect of Th1 cells at the periphery (that uses NEUTROPHILS)

A
  • NEUTROPHILS are activated using TNF alpha (increased inflammation and microbial killing)
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20
Q

how do Th1 cells activate NK cells and CD8+ T cells

A

Th1 cells produce INTERFERON GAMMA which activates NK cells and CD8+ T cells which helps kill virally infected cells

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21
Q

what is the role of Th1 cells in the secondary lymphoid tissue

A
  • produce INF-gamma which acts on B cells causing them to produce different IMMUNOGLOBULINS (IgG3 and IgG2a) which INC OPSONISATION and PHAGOCYTOSIS of microbes
  • O allowing the macrophages to engluf the microbes more easily
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22
Q

briefly summaraise the 4 effector mechanisms of Th1 cells

A

1) in 2ndary lympohoid tissue, they release IFN-gamma which causes B cells to produce IgG3 and IgG2a which inc OPSONISATION and PHAGOCYTOSIS of microbes
2) in the PERIPHERY NEUTROPHILS are activated using TNF alpha (increased inflammation and microbial killing)
3) in the PERIPHERY CD40 LIGAND (CD40 L ) on T cell interacts with CD40 on APC induces macrophage to be BETTER AT KILLING the microbe it has phagocytosed
4) produce INTERFERON GAMMA which activates NK cells and CD8+ T cells which helps kill virally infected cells

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23
Q

what immune response do Th2 cells promote

A

humoral immune response

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24
Q

Th2 cells interact with B cells causing what

where does this occur

A
  • in the secondary lymphoid tissue
  • CD40L on Th2 binds to CD40 on B CELL
  • and IL-4 production causes
  • this causes the production of neutralising IgG antibodies (IgG4 human and IgG1 in mice) IMPORTANT for binding to SMALL soluble particles eg TOXINS so they can be NEUTRALISED
  • also causes the production of IgE which is important in MAST CELL DEGRANULATION which can bind to PARASITES and HELMINTHS
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25
Q

what effect do Th2 cells have on IL-5

A
  • Th2 cells release IL-5 causing ACTIVATION of EOSINOPHILS which can RECOGNISE OPSONISED HELMINTHS/PARASITES
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26
Q

are the released factors of mast cells and eosinophils targeted/general

A

GENERAL: O they can act on self cells as well, which are responsible for causing the ‘allergic’ reaction

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27
Q

how can Th2 cells essentially turn off the Th1 cell response

A
  • by releasing IL-10 and IL-4 which act in the PERIPHERY to cause the SUPRESSION OF MACROPHAGE ACTIVATION
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28
Q

briefly summarise the effector mechanisms of Th2 cells

A

1) in 2ndary lymphoid tissues the binding of CD40L to CD40 on B CELLS as well as IL-4 production causes the production of NEUTRALISING IgG antibodies (which target small things eg TOXINS) and production of IgE which causes MAST CELL DEGRANULATION–> HELMINTHS/PARASITES
2) release IL-5 in the PERIPHERY ACTIVATION of EOSINOPHILS which can RECOGNISE OPSONISED HELMINTHS/PARASITES
3) releasing IL-10 and IL-4 which act in the PERIPHERY to cause the SUPRESSION OF MACROPHAGE ACTIVATION

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29
Q

what is the role of Th17 cells

A

they are important in protection against bacteria in MUCOSAL SURFACES (eg gut)
- eliminate extracellular bacteria and fungi

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30
Q

explain in detail what effect

A
  • in the 2ndary lymphoid, the effector cells then move to the PERIPHERAL to the MUCOSAL surface
  • here they release IL-17 and IL-22
  • IL-17 is a potent inducer of INFLAMMATION and causes NEUTROPHILS to be attracted to the site
  • neutrophils then clear the bacteria (O help epi produce antimicrobial peptides)
  • IL- 22 also helps the epi prod antimicrobial peptides
  • it INCREASES the BARRIER function of EPITHELIAL surface O there are fewer leaks O bacteria cannot enter tissue
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31
Q

what is the role of the Tfh cells

what do they develop with

A
  • can ACTIVATE B cells to PROLIFERATE and DIFFERENTIATE into Ab
  • develop in concert with Th1, Th2 and Th17 cells
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32
Q

what is class switching and what do Tfh have to do with it

A

CLASS SWITCH: They help B cells to generate different Ig isotypes and undergo affinity maturation in the germinal centre

33
Q

which Ig isotype and O FC receptor depends on what

A

depends on the most appropriate innate immune effector interaction

34
Q

why are Tfh cells unlike the other Th cells

A

unlike Th1, Th2 and Th17, Tfh cells contribute to the eradication of most classes of pathogens
O involved in ALL TYPES OF IMMUNE RESPONSES

35
Q

where do all the functions of Tfh occur

A

in 2ndary lymphoid organs, as they direct the B cell response

36
Q

how do Tfh cause class switching

A
  • B cell binds Ag and take it up (phagocytose)
  • then present via MHC II to Tfh
  • Tfh via CD40L and IL-21 ACTIVATE B cell and make it produce diff type of Ig and CAUSE ISOTYPE SITCHING AND AFFINITY MATURATION
37
Q

give example of responses that Tfh are involved in

explain why

A
  • allergic response
  • cell mediated response
  • Th17
    as it CHANGES what AB (via class switching) are produced
38
Q

where do Tregs (T regulatory cells) work

A

2ndary lymphoid and periphery

39
Q

what are the functions of Tregs

A

1) produce ANTI-INFLAMMATORY cytokines
2) provide CTLA-4 which engages CD8-/86 during ANERGY
3) Tregs ‘rip off’ and ENDOCYTOSE CD80/86

40
Q

which inflammatory cytokines does Tregs produce

A
  • TGF beta

- IL-10

41
Q

why is CTLA-4 important

A
  • CTLA-4 is expressed on the naive T cell
  • it interacts with CD80/86 INSTEAD of C28
  • O BLOCKS the co-stimulatory signal, and you dont get activation of an effector response
42
Q

how can Tregs affect CD80/86

A
  • they can rip off and ENDOCYTOSE CD80/86
43
Q

which cytokines does Th1 release

A

IFN gamma

44
Q

which cytokines does Th2 release

A

IL-4, Il-5

45
Q

which cytokines does Treg release

A

IL-10, TGF beta

46
Q

which cytokines does Th17 release

A

IL-17

47
Q

which cytokines does Tfh release

A

IL-21

48
Q

what are the key Th cells

A

1,2,17, fh and Treg

49
Q

how are T cells in circulation directed to the right part of the body

A

by the interaction between MOLECULES ON T CELLS and on ENDOTHELIAL CELLS lining the blood vessels

50
Q

what is the role of cytokines in T cell migration

A
  • produced by the innate immune system

- the UPREGULATE ADHESION MOLECULE EXPRESSION on the endothelium to INITIATE MIGRATION

51
Q

what are chemokines

A

a type of cytokine that attracts cells to PARTICULAR SITES

52
Q

where do CD8 + T cells carry out their functions

A

at the periphery, at the exact place that pathogens are

53
Q

what directs whether a T cell needs to go to the periphery or to the lymph node

A

chemokine gradients

54
Q

what are thesteps in T cell migration

A

1) start with ROLLING, LOOSE adhesion, controlled by SELECTINS
2) then the CHEMOKINES cause ACTIVATION of intergrins on T cell (a more FIRM interaction between endothelium and T cell)
3) there is then a STABLE ARREST guided by INTEGRINS
4) then the T cell follows the CHEMOKINE GRADIENT
5) there is then EXTRAVASATION/MIGRATION

55
Q

what is T cell migration directed by

A

adhesion molecules

56
Q

where do naive T cells need to migrate between

A

between lymph nodes where they may come into contact w/ APCs

O to enter the lymph node they need to pass the HEV

57
Q

to enter to HEV what selectins, chemokines, integrins and chemokines does the naive T cell express

A
  • L-selectin
  • CC21 chemokine
  • LFA-1 integrin
  • CC21, CC12 chemokines
58
Q

where do the effector T cells need to enter

A

they need to enter the infected tissue

59
Q

which selectin, chemokine and integrins do effector T cells use

A
  • E and P-selectin
  • CXCL10 chemokines
  • LFA-1 and VLA-4 integrin
60
Q

when and why do T cells alter their adhesion molecule expresion

A

AFTER ACTIVATION to an EFFECTOR CELL and differentiation (because effector cells need to go to the site of infection)

61
Q

what determines adhesion molecule expression on T cells

A
  • partly determined by the APC

- O the APC helps direct the effector T cell to correct tissue

62
Q

what are the 4 key steps of T cell migration

A

1) rolling
2) activation by chemokines
3) adhesion
4) extravasation

63
Q

what mediates T cell migartion

A

1) selectins (rolling)
2) integrin (firm adhesion)
3) chemokines
4) integrin activation

64
Q

CD8 T cell killing is what

A

SPECIFIC: target cell must bear the SAME antigen that activated the naive CD8 + T cell presented in MHC I on its surface

CD8+ T cell must CONTACT the target cell

CD8+ T cells REMAIN INTACT after they kill target cells, each is capable of killing may target cells

65
Q

what is CTL

A

cytotoxic T lymphocytes

66
Q

how does a CD8+ cell cause cell death

A
  • causes DNA FRAGMENTATION
67
Q

what are the 2 mechanisms used by CD8+ to induce cell death

A

1) GRANZYME/PERFORIN granules (used most commonly)

2) Fas-Fas ligand

68
Q

describe GRANZYME/PERFORIN granules as a method of killing used by CD8+ T cells

A

1) MHC I and TCR interact forming IMMUNOLOGICAL SYNAPSE
2) causes release of granules which act ONLY on the target cell
3) perforin punches a hole in the bilayer, allwoing granzymes into the cytosol, which…
4) causes CASPASE activation
5) causes APOPTOSIS

69
Q

describe Fas-Fas ligand as a method of killing used by CD8+ T cells

A

1) Fas ligand on T cell interacts w/ Fas on target cell
2) causes CASPASE activation
3) causes APOPTOSIS

70
Q

why is it important that CD8+ T cells kill and induce detah via APOPTOSIS and NOT NECROSIS

A
  • necrosis can cause uncontrolled release of material (you are exposing pathogen to healthy tissue)
  • apoptosis is controlled
71
Q

what is the TCR, antigen, MHC, location, main target, and function of γδ T cells

A

TCR: γδ
ANTIGEN: non peptide, lipid
MHC: independent (like PRR)/MHC like proteins
LOCATION: skin, mucosal lymphoid tissue, blood
MAIN TARGET: Bacterial infections, pathogenic toxins, stress markers
FUNCTION: Cytotoxicity (perforin/granzyme) and cytokines (IFNγ, TNFα and IL-17). Can phagocytose

72
Q

what is the TCR, antigen, MHC, location, main target, and function of iNKT T cells

A

TCR: iα:β
ANTIGEN: Microbial lipid
MHC: CD1
LOCATION: Mucosal surface
MAIN TARGET: Infected/ transformed cells (low does bacterial infections
FUNCTION: Cytotoxcity (mainly Fas:FasL) and cytokine (e.g. IL-2/TNFα

73
Q

what is the TCR, antigen, MHC, location, main target, and function of general T cells

A

TCR: α:β
ANTIGEN: peptide
MHC: MHC I/II
LOCATION: Lymph, peripheral tissue, blood
MAIN TARGET: infected/transformed cells
FUNCTION: Cytotoxcity (perforin /granzyme and Fas:FasL) and determining immune response (cytokines)

74
Q

γδ and iNKT T cells are innate or adaptive?

A

somewhere in between

75
Q

what are the 5 stages of T cell response

A

1) antigen recognition
2) activation
3) antigen elimination
4) contraction/homeostasis
5) memory

76
Q

what happens during contraction/homeostasis

A
  • stimulus for co-stimulation DEC
  • new effector cells are NOT activated
  • effector cells AGE and die by apoptosis and are cleared by PHAGOCYTES
    (alost 95% of T cells die once antigen is eliminated)
77
Q

what happens to the effector T cells that are not killed by apoptosis

A

some stay in lymph node, some stay in peripheral tissue

78
Q

how do memory T cells form

A
  • Some of the progeny of antigen-stimulated T cells develop into long-lived, functionally quiescent (‘resting’) memory cells
  • Memory T cells are responsible for accelerated and enhanced secondary immune responses on subsequent exposures to the same antigen
79
Q

which cytokines are req for polarisation of Th17

A

IL-1, IL-6, TGF BETA

YEAR 2 S2 IMMUNO (14 decks)

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