B & I - Cell Mediated Immunity and MHC

Question 1

where do immature lymphocytes from bone marrow travel to to mature

Answer 1

thymus

Question 2

what surface antigens are expressed in this immature stage

Answer 2

CD4 and CD8

Question 3

they encounter MHC ______ __ and _____ __ molecules expressed on thymic epithelium and respond accordingly or die by neglect

Answer 3

class I and class II

Question 4

If they respond to MHC class II they become?

Answer 4

CD4 helper T cells

Question 5

If they respond to MHC class I they become?

Answer 5

CD8 cytotoxic T cells (CTL) and their fate is sealed in the thymus before they exit into the blood stream

Question 6

what do the CD4 helper cells do

Answer 6

respond by secreting cytokines

Question 7

what do the CD8 cytotoxic cells do

Answer 7

kill other infected cells

Question 8

what are the 4 subsets of CD4 helper

Answer 8

treg
Th1
Th2
Th17

Question 9

what does treg do

Answer 9

suppresses the immune response

Question 10

what does Th1 do

Answer 10

promotes cell-mediated immunity

Question 11

what does Th2 do

Answer 11

promotes antibody mediated immunity

Question 12

what does Th17 do

Answer 12

promotes inflammation

Question 13

what type of organ is the thymus and when is it the largest

Answer 13

it is a primary lymphoid organ that is largest at birth and shrinks with age

Question 14

where is the thymus located

Answer 14

sits at the top of the pericardium above the heart

Question 15

haemopoietic lymphoid precursors migrate from the bone marrow to the thymus where they mature into ?

Answer 15

T lymphocytes

Question 16

only a small percentage of T cells survive the thymus as mature T cells, most die from

Answer 16

neglect

Question 17

T cell that survive the thymus have been educated to do what

Answer 17

educated to recognise self MHC molecules expressed in thymic tissue

Question 18

viruses replicate ____ cells

Answer 18

inside

Question 19

immune system is regulated by a set of?

what do these genes make up

Answer 19

highly polymorphic genes that were first identified as controlling tissue transplantation - these genes make up the MHC (Major Histocompability Complex)

Question 20

what do these genes code for

Answer 20

human leukocyte antigens (HLA ) on the cell surface

Question 21

unlike antibodies, the TcR recognises only ___ antigen

Answer 21

one

Question 22

what antigen does the TcR recognise and why

Answer 22

the proteins of the MHC because the T cells were selected during thymic development for their ability to respond to self MHC molecules

Question 23

unlike Ig, the TcR (does/does not?) under go affinity maturation

Answer 23

does not

Question 24

why does TcR not undergo affinity maturation

Answer 24

because you don’t want the affinity of TcR to increase to a self antigen

Question 25

When do cytotoxic T cells (CTL) react to your own cells

Answer 25

when there is a change in MHC class I molecules - i.e. when the express a "neo-antigen" picked up from inside the cell

Question 26

the "neo-antigen" can be a ____ or _____ ___ antigen

Answer 26

viral | altered self

Question 27

what do histocompatibility genes control

Answer 27

viral immunity

Question 28

what are the two antigens viral immunity requires

Answer 28

self and non-self

Question 29

what are self antigens

Answer 29

antigens encoded by MHC

Question 30

what are non-self antigens

Answer 30

antigens encoded by the virus

Question 31

what do T cells detect

Answer 31

small fragments of virus picked up inside the cell and expressed in the binding groove of MHC molecules on the cell surface

Question 32

viral immunity depends on ____ to present antigens

Answer 32

MHC

Question 33

what is the T cell receptor

Answer 33

a membrane bound Ig-like molecule on T lymphocytes

Question 34

HLA molecules are expressed on most cells and present what to T cells?

Answer 34

peptide antigens

Question 35

Are HLA molecules polymorphic

Answer 35

yes they are highly polymorphic

Question 36

what does the antigen binding surface of the TcR bind to

Answer 36

the top of MHC which represent the "peptide groove"

Question 37

what does the peptide groove contain

Answer 37

the foreign peptide antigen

Question 38

the TcR has affinity towards ?

Answer 38

the combination of MHC

Question 39

MHC refers to ?

Answer 39

the genetic locus that regulates histocompatibility

Question 40

HLA refers to ?

Answer 40

the 6 different molecules expressed on human cells

Question 41

H2 refers to ?

Answer 41

the antigens on mouse cells

Question 42

What are the three human Class I molecules

Answer 42

A B C

Question 43

what are the three human class II molecules

Answer 43

DR, DP, DQ

Question 44

what are CD4 and CD8

Answer 44

accessory molecules that physically associate with the TcR

Question 45

what do CD4 helper T cells do in this context

Answer 45

recognise antigens in MHC class II

Question 46

what do CD8 cytotoxic T cells

Answer 46

recognise antigens in MHC class I

Question 47

what component of CD4 and CD8 initiates T cell signalling

Answer 47

CD4 and CD8 have intracellular tyrosine kinases associated with their cytoplasmic tails that initiate T cell signalling through phosphorylation.

Question 48

what are CD4 and CD8 crucial for

Answer 48

immune activation

Question 49

CD4 and CD8 are ___________ that define two ______ _______ __ _ __________

Answer 49

co-receptors important subsets of T lymphocytes

Question 50

peptide source of MHC class I

Answer 50

intracellular

Question 51

pathogen in MHC class I

Answer 51

viruses

Question 52

responding T cells in MHC class I

Answer 52

CD8

Question 53

effector function of MHC class I

Answer 53

cytotoxic

Question 54

Peptide source of MHC class II

Answer 54

extracellular

Question 55

pathogen of peptide source MHC class II

Answer 55

bacteria

Question 56

responding T cells of MHC class II

Answer 56

CD4

Question 57

effector function of MHC class II

Answer 57

help

Question 58

T cells ______ and produce _______ that ____ other cells

Answer 58

proliferate produce help

Question 59

what does CTL produce that punches holes and destroys cell viability (and what does it punch holes in)

Answer 59

CTL produces granzyme and perforins that punch holes in the target cell membrane and destroy cell viability

Question 60

there are hundreds of different amino acid variations at each ____ _______

Answer 60

MHC locus

Question 61

polymorphism is restricted to

Answer 61

the protein domains that form the peptide groove

Question 62

what genes and molecules does an individual express

Answer 62

both maternal and paternal genes 2 x 3 MHC class I A B C and 2 x 3 MHC class II DR DP DQ molecules

Question 63

how are the genes and molecules in an individual expressed

Answer 63

with co-dominance

Question 64

how many polymorphic molecules are expressed on cells

Answer 64

12

Question 65

can two people have the same MHC profile

Answer 65

no everyone is completely different (identical twins excluded)

Question 66

why can't tissue be transplanted from one person to another

Answer 66

because of MHC polymorphism - T cells from the recipient recognise the donor MHC antigens as foreign

Question 67

what must people who get transplants do

Answer 67

take an immunosuppressive drug for the rest of their lives to suppress the T cell response

Question 68

what are the two major consequences of MHC polymorphism

Answer 68

1) tissue transplantation is difficult except for identical twins. this requires careful matching and immunosuppressive drugs. 2) MHC polymorphism are strongly linked to many autoimmune diseases.

Question 69

why is MHC so strongly associated with many autoimmune diseases

Answer 69

because the MHC locus is the only polymorphic part of your entire genome

Question 70

in autoimmune disease, what are your T cells doing?

Answer 70

reacting to self-antigens that are best presented by these MHC molecules

Question 71

MAIN POINT: what is MHC

Answer 71

a set of highly polymorphic genes coding for a group of membrane molecules called HLA in humans

Question 72

MAIN POINT: the TcR is an Ig like membrane molecule with a gene locus that is

Answer 72

segmented and undergoes rearrangement

Question 73

MAIN POINT: Graft rejection was used to create? what did this show?

Answer 73

congenic strains of mice that were then used in a famous experiment showing that viral immunity requires both self MHC and foreign antigen

Question 74

MAIN POINT: MHC molecules come in which two types and what do both have

Answer 74

class I and class II both have a peptide binding groove that holds a foreign peptide

Question 75

MAIN POINT: T cells are divided into two functionally different populations marked by the?

Answer 75

CD4 and CD8 antigens

Question 76

MAIN POINT: CD4 and CD8 are accessory molecules associated with the T cell receptor responsible for

Answer 76

intracellular signalling through associated tyrosine kinases

Question 77

MAIN POINT: CD8+ T cells are _____ and recognise _____ antigens presented by MHC class _

Answer 77

cytotoxic viral antigens MHC class I

Question 78

MAIN POINT: CD4+ T cells are _____ ___ ___ and recognise _____ antigens presented by MHC class _

Answer 78

helper T cells bacterial antigens MHC class II

Question 79

MAIN POINT: why is tissue transplantation so difficult

Answer 79

MHC polymorphism

Question 80

MAIN POINT: Why are MHC polymorphisms so strongly linked to many disease susceptibilities

Answer 80

because it is the only part of your genome that is so polymorphic