antigen presentation and T lymphocytes

Question 1

what does CD stand for

Answer 1

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

Question 2

what is the function of CD8+ CTL cells

Answer 2

cytotoxic so kill target cells, secrete cytokines

Question 3

what is the function of CD4+ Th1 cells

Answer 3

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

Question 4

what is the function of CD4+ Th2 cells

Answer 4

stimulate B cell proliferation

Question 5

what does the TCR resemble

Answer 5

antibody Fab fragment; analogous to Fc of antibody

Question 6

what does the TCR consist of

Answer 6

2 chains consisting of variable and constant domains

Question 7

structure of TCR

Answer 7

diagram from TCR

Question 8

what do all TCR express

Answer 8

CD3 polypeptides

Question 9

what type of TCR do most T cells have

Answer 9

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

Question 10

what other type of TCR can be present on T cells

Answer 10

yd

Question 11

what two types of CD4+ T cells are there

Answer 11

T helper and T regulatory

Question 12

what antigen do T cells only recognise

Answer 12

processed antigen on antigen presenting cell by MHC

Question 13

what MHC class are CD4 restricted to

Answer 13

MHC class II

Question 14

what MHC class are CD8 restricted to

Answer 14

MHC class I

Question 15

where to T cells originate and mature

Answer 15

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

Question 16

process of maturation in thymus

Answer 16

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

Question 17

maturation in thymus: positive selection

Answer 17

survival with TCR which recognises self MHC

Question 18

maturation in thymus: negative selection

Answer 18

removal with TCR which recognises self MHC too strongly

Question 19

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

Answer 19

autoimmune diseases

Question 20

what is thymus selection -1

Answer 20

if new B chain is not functional, apoptosis occurs

Question 21

what is thymus selection -2

Answer 21

is aB TCR functional, dangerour or autoreactive

Question 22

TCR polymorphism

Answer 22

diversity exists within an individual

Question 23

what are naive T cells

Answer 23

mature recirculating T cells that have not yet encountered an antigen

Question 24

what are effector T cells

Answer 24

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

Question 25

what are memory T cells

Answer 25

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

Question 26

T cell recirculation pathway and how do they move

Answer 26

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

Question 27

why do T cells recirculate

Answer 27

increases likelihood of encountering antigen

Question 28

5 stages of cell mediated immunity

Answer 28

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

Question 29

what are the 3 signal models for T cell activation

Answer 29

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

Question 30

CD8+ effector functions

Answer 30

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

Question 31

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

Answer 31

perforin, granzymes, granulysin

Question 32

cell mediated cytotoxicity: what type of cell death is achieved

Answer 32

apoptosis

Question 33

cell mediated cytotoxicity: what happens to nuclear DNA

Answer 33

fragmented

Question 34

cell mediated cytotoxicity: what does perforin do

Answer 34

punches hole in infected cell membrane

Question 35

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

Answer 35

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

Question 36

what do CD4+ cells produce to shape downstream responses

Answer 36

different restricted cytokine patterns

Question 37

what does CD4+ Th1 produce

Answer 37

interferon gamma to boost IC immune response by recruiting macrophages

Question 38

what does CD4+ Th2 produce

Answer 38

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

Question 39

what is the function of Th17

Answer 39

protect against some bacterial infections, mediate autoimmune response

Question 40

what is the function of Treg

Answer 40

inhibit activation of naive and effector cells by contact or cytokines

Question 41

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

Answer 41

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

Question 42

why do inflammatory Th1 effector cells activate macrophages

Answer 42

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

Question 43

what is delayed type hypersensitivity associated with

Answer 43

allergy

Question 44

what is delayed type hypersensitivity

Answer 44

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

Question 45

what are the 2 phases of delayed type hypersensitivity

Answer 45

sensitisation and effector

Question 46

delayed type hypersensitivity: sensitisation

Answer 46

must be exposed to antigen first before becoming allergic to it

Question 47

delayed type hypersensitivity: effector

Answer 47

on second exposure you can trigger a severe response

Question 48

how do T cells enable other cells to function

Answer 48

better digestion by engaging macrophage, better killing

Question 49

B cell activation: what is the purpose

Answer 49

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

Question 50

B cell activation: how do T cell intstruct B cells

Answer 50

trigger expression of CD40 ligand on T cells to secrete cytokines

Question 51

what is the purpose of immunological memory

Answer 51

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

Question 52

do T cells undergo isotype switching or affinity maturation

Answer 52

no

Question 53

T memory cell activation

Answer 53

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

Question 54

what T cell memories are bad

Answer 54

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

Question 55

when does T cell exhaustion occur

Answer 55

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

Question 56

how does T cell exhaustion occur

Answer 56

CD8 pool contracts to prevents excess damage; | PD-1 marker makes T cell harder to activate, and these are expressed more as more proliferate