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Immunology > 4. T cells > Flashcards

4. T cells Flashcards

1
Q

importance of T cells

A

aid the clearance of intracellular microbes in macrophages (cell mediated immunity)
help B cells produce different Ig isotypes and high affinity antibodies
recognise virally infected cells and kill them

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2
Q

t cell development process

A
  1. peptide antigen recognition via APCs
  2. clonal expansion
  3. differentiation
  4. activation
  5. antigen elimination
  6. apoptosis
  7. surviving memory cells
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3
Q

central tolerance

A

negative selection and apoptosis of t cells that recognise self cells to prevent autoimmunity
occurs in the thymus

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4
Q

naive cells

A

have not been stimulated by antigen

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5
Q

effector cells

A

specialised functions incl. cytokine secretion and cytotoxic activity

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6
Q

memory cells

A

had antigen presented to them and remain in immune system to be subsequently reactivated if needed

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7
Q

migration of naive, effector and memory t cells

A

lymph nodes
inflamed tissues
both

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8
Q

frequency of cells for specific antigens (naive, effector, memory)

A

very low
high (clonal expansion)
low (mostly apoptosed)

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9
Q

which mhc class types do helper cells and cytotoxic cells recognise

A

helper - 2 (exogenous)

cytotoxic - 1 (endogenous)

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10
Q

t cell activation

A

requires two signals - from antigen and co-stimulatory molecules
then able to undergo clonal expansion

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11
Q

which cytokine is produced by the second signal

A

IL-2 to induce proliferation by autocrine action

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12
Q

examples of co-stimulators

A

CD80/86 or B7 on DCs to bind to CD28 receptors on t cell

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13
Q

what is the most potent stimulator of naive t cells

A

dendritic cells - express the highest levels of co-stimulators

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14
Q

immature vs mature DCs

A

immature - Ag uptake mode, non-motile, MHC low, highly phagocytic, B7 low

mature - Ag presentation mode, motile, MHC high, poorly phagocytic, B7 high

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15
Q

t cell activation vs anergy

A

activation: APC increased expression of co-stimulators and cytokine production
anergy: APC in resying state, no co-stimulator expression

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16
Q

peripheral tolerance

A

t cell anergy if self-antigen recognition by engagement of inhibitory CTLA4 receptors

17
Q

t cell assistance in peripheral tolerance

A

Tregs provide CTLA4 which engages B7 instead of CD28 to stop activation

18
Q

different types of t cell

A

helper (1, 2, 17, regs, follicular)
cytotoxic
invariant NKT
gamma/delta

19
Q

functions of t cells

A 
help b cells - class switching and affinity maturation
kill infected cells
secrete cytokines
tolerance to prevent autoimmunity
activate macrophages and neutrophils
20
Q

how many signals needed for t cell differentiation

A

3 - same two as activation and proliferation as well as a third (cytokines) for differentiation

21
Q

which cytokines are produced by apcs for t cell differentiation

A

IL4, 6, 12, 23

22
Q

t cell polarisation

A

cytokines produced by apcs induce t cell differentiation into a specific helper subtype

23
Q

th1 vs th2

A

1: cell mediated; bacteria, virus, fungi; IL-12; STAT4; T-bet
2: humoral; parasites, worms; IL-4; STAT6; GATA-3

24
Q

cytotoxic t cell activation

A

also requires 2 signals but needs more co-stimulation provided by Th1 or 17 which produce CD40L and IL-2

25
Q

CD40L

A

binds to CD40 on APC to make more CD80/86

26
Q

cross presentation

A

presentation of exogenous antigen to MHC1 (usually for endogenous) by being loaded with MHC1 proteins

27
Q

Th1

A

inflammatory, produce TNFa, activate macrophages, NKs and Tc, intracellular pathogens, increase IgG3&2a for opsonisation

28
Q

Th2

A

mast cell, eosinophil, b cell activation for neutralisation of toxins, IgE, worms, allergies, parasites, suppress macrophages

29
Q

Treg

A

anti inflammatory, homeostasis, peripheral tolerance, suppresses immune responses, provide CTLA4 for anergy, endocytose CD80/86

30
Q

Th17

A

pro-inflammatory, mucosal immunity, bacteria and fungi, recruit neutrophils and monocytes, maintain epithelial barrier

31
Q

Tfh

A

antibody production, in lymph node follicles, class switching and affinity maturation, eradicate most pathogen classes

32
Q

how do t cell migrate around the body

A

adhere to endothelial cells in blood vessels and roll along, attracted by chemokines and cytokines, enter by extravasation/diapedesis
aka cell homing

33
Q

selectins vs integrins

A

rolling effect

adhesion effect

34
Q

mechanisms of Tc killing

A

granzymes/perforins
fas-fas ligands (on Tc and target)

both induce apoptosis by caspase activation

Immunology (9 decks)

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