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MCD Immunology > antigen presentation and T lymphocytes > Flashcards

antigen presentation and T lymphocytes Flashcards

T lymphocyte subsets: summarise the origins and functions of T lymphocyte subsets

1
Q

what does CD stand for

A

cluster of differentiation (cell surface molecules present on wide variety of cells)

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2
Q

what is the function of CD8+ CTL cells

A

cytotoxic so kill target cells, secrete cytokines

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3
Q

what is the function of CD4+ Th1 cells

A

secrete cytokines for recruiting cells, delayed type hypersensitivity, activating macrophages or amplifying CTL and B cell responses

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4
Q

what is the function of CD4+ Th2 cells

A

stimulate B cell proliferation

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5
Q

what does the TCR resemble

A

antibody Fab fragment; analogous to Fc of antibody

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6
Q

what does the TCR consist of

A

2 chains consisting of variable and constant domains

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7
Q

structure of TCR

A

diagram from TCR

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8
Q

what do all TCR express

A

CD3 polypeptides

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9
Q

what type of TCR do most T cells have

A

aB (2/3 CD4, 1/3 CD8)

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10
Q

what other type of TCR can be present on T cells

A

yd

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11
Q

what two types of CD4+ T cells are there

A

T helper and T regulatory

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12
Q

what antigen do T cells only recognise

A

processed antigen on antigen presenting cell by MHC

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13
Q

what MHC class are CD4 restricted to

A

MHC class II

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14
Q

what MHC class are CD8 restricted to

A

MHC class I

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15
Q

where to T cells originate and mature

A

originate in bone marrow, pass as progenitor cells to thymus to mature

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16
Q

process of maturation in thymus

A

enter as CD4- and CD8- (no TCR so are double negative) → attempt to create TCR by recobination of gene segments in cortex (CD4- CD8- preTCR+; preTCR consists of B and surrogate aTCR) → CD4+ CD8+ TCR+ (double positive) → either become CD4+ TCR+ or CD8+ TCR+ in medulla

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17
Q

maturation in thymus: positive selection

A

survival with TCR which recognises self MHC

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18
Q

maturation in thymus: negative selection

A

removal with TCR which recognises self MHC too strongly

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19
Q

if TCR is produced which binds too tightly, what can occur

A

autoimmune diseases

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20
Q

what is thymus selection -1

A

if new B chain is not functional, apoptosis occurs

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21
Q

what is thymus selection -2

A

is aB TCR functional, dangerour or autoreactive

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22
Q

TCR polymorphism

A

diversity exists within an individual

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23
Q

what are naive T cells

A

mature recirculating T cells that have not yet encountered an antigen

24
Q

what are effector T cells

A

T cells that have encountered an antigen, proliferated and differentiated into cells that participate in host defence

25
Q

what are memory T cells

A

T cells that have encountered an antigen, contracted, and are ready to respond to future infections

26
Q

T cell recirculation pathway and how do they move

A

migration of T cells from lymph node into blood to lymphoid organs via high endothelial venules; move via chemokine gradient or by adressins and integrins

27
Q

why do T cells recirculate

A

increases likelihood of encountering antigen

28
Q

5 stages of cell mediated immunity

A

APC collects material → MHC:peptide TCR interaction → naive T cell becomes effector → effector recognises MHC:peptide on infected cell and performs function → effector pool contracts to memory state for secondary immune response

29
Q

what are the 3 signal models for T cell activation

A

antigen recognition (requires MHC:peptide), co-stimulation, cytokine release

30
Q

CD8+ effector functions

A

cytotoxic T cells so target and kill infected cells; recognise MHC class I

31
Q

cell mediated cytotoxicity: what 3 things are present in cytotoxic granules

A

perforin, granzymes, granulysin

32
Q

cell mediated cytotoxicity: what type of cell death is achieved

A

apoptosis

33
Q

cell mediated cytotoxicity: what happens to nuclear DNA

A

fragmented

34
Q

cell mediated cytotoxicity: what does perforin do

A

punches hole in infected cell membrane

35
Q

cell mediated cytotoxicity: what induces cell death and how is this achieved

A

FasL on CD8 induces cell death by interacting with Fas on target cells; both upregulate CASPASE which drives apoptosis

36
Q

what do CD4+ cells produce to shape downstream responses

A

different restricted cytokine patterns

37
Q

what does CD4+ Th1 produce

A

interferon gamma to boost IC immune response by recruiting macrophages

38
Q

what does CD4+ Th2 produce

A

IL-4, IL-5 and IL-13 to boost anti-multicellular organism response

39
Q

what is the function of Th17

A

protect against some bacterial infections, mediate autoimmune response

40
Q

what is the function of Treg

A

inhibit activation of naive and effector cells by contact or cytokines

41
Q

what are the 3 effector functions of CD4+ Th1 effector cells

A

macrophage activation, delayed type hypersensitivity (also Th2 for multicellular), B cell activation

42
Q

why do inflammatory Th1 effector cells activate macrophages

A

to promote killing of IC pathogens; cross talk between T cell and macrophages by cytokines

43
Q

what is delayed type hypersensitivity associated with

A

allergy

44
Q

what is delayed type hypersensitivity

A

cell-mediated response with main role of defence against IC pathogens; if source of antigen is not eradiacted, chronic stimulation and granuloma formation occur; if antigen is not a microbe, delayed type hypersensitivity produces tissue injury without protection

45
Q

what are the 2 phases of delayed type hypersensitivity

A

sensitisation and effector

46
Q

delayed type hypersensitivity: sensitisation

A

must be exposed to antigen first before becoming allergic to it

47
Q

delayed type hypersensitivity: effector

A

on second exposure you can trigger a severe response

48
Q

how do T cells enable other cells to function

A

better digestion by engaging macrophage, better killing

49
Q

B cell activation: what is the purpose

A

B and T cell recognise same antigen; T cell instructs B cell to be activated and make antibodies

50
Q

B cell activation: how do T cell intstruct B cells

A

trigger expression of CD40 ligand on T cells to secrete cytokines

51
Q

what is the purpose of immunological memory

A

more rapid and heightened so prevent disease and can confer life-long immunity to many infections; basis for vaccines

52
Q

do T cells undergo isotype switching or affinity maturation

A

no

53
Q

T memory cell activation

A

less stringent so proliferate faster and express different chemokine receptors compared to naive T cells

54
Q

what T cell memories are bad

A

target self (autoimmune) or target benign antigens (allergy)

55
Q

when does T cell exhaustion occur

A

if source of antigen remains, constant T cell proliferation which can be dangerous, so is shut down over time (e.g cancer)

56
Q

how does T cell exhaustion occur

A

CD8 pool contracts to prevents excess damage;

PD-1 marker makes T cell harder to activate, and these are expressed more as more proliferate

MCD Immunology (23 decks)

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