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Immunology Block 1 > Ppt 3 antigen capture and presentation > Flashcards

Ppt 3 antigen capture and presentation Flashcards

1
Q

How are the adaptive immune responses initiated?

A

When in presence of antigen

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2
Q

Do lymphocytes of adaptive immunity recognize same antigen?

A

no

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3
Q

What to antigen receptors on B lymphocytes recognize?

A

all types of molecules of antigen: carbs/lipids/protein

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4
Q

what do antigen receptors on T lymphocytes recognize?

A

only peptide antigen

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5
Q

What is used by dendritic cells topresent peptide antigen to T lymphocytes?

A

MHC

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6
Q

Do all dendritic cells need to use MHC molecules to present peptide antigen to T lymphocytes?

A

yes

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7
Q

what is the MHC?

A

a genetic locus that works by binding peptide antigen

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8
Q

what is MHC restriction?

A

T cells will recognize peptides only when they are presented by your own MHC molecules

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9
Q

Why do T cells have dual specificity?

A

because they recognize theMHC molecule doing the presentingand the peptide being presented

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10
Q

How do peptides bind to the MHC molecule?

A

through anchor residues

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11
Q

blood borne antigen are taken where?

A

captured by APC ‘s and taken to the spleen

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12
Q

antigen in epithelium or connective tissue are taken where?

A

lymph nodes

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13
Q

What cell mainly captures antigen and where does it take it?

A

dendritic cell and it takes and accumulates it in the lymph nodes

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14
Q

dendritic cells capture antigen and present it to whom?

A

Naive T cells

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15
Q

Once Naive T cells have been presented the antigen by dendritic cells, what happens to them?

A

they will start clonal expanssion and effector differentiation

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16
Q

where do we find immature dendritic cells?

A

in the epithelium

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17
Q

where do we find mature dendritic cells?

A

in the paracortex

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18
Q

once a naive t cell has differentiated and divided, it leaves the lymph organ and now has to find what?

A

the same antigen peptide it was presented by the dendritic cell

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19
Q

Give an example of a immature dendritic cell

A

langerhans cell

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20
Q

why are immature dendritic cells “immature”?

A

They are inefficient at stimulating T cellsbecause they do not have the necessary things required to stimulate T cells

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21
Q

Immature dendritic cells express this receptor to bind microbes

A

receptor for terminal mannose residues

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22
Q

how do microbes stimulate the innate immunity?

A

by stimulating Toll-like receptors in dendritic cells, resident macrophages and epithelial cells, leading to secretion of TNF and IL-1 (inflammation)

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23
Q

what activates dendritic cells?

A

cytokines and toll-like receptors

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24
Q

what do mature dendritic cells express on their surface?

A

MHC and co-stimulators (B7)

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25
Q

When dendritic cell encounters and binds antigen, where do they go? what is expressed in order for the dendritic cell to go there?

A

they go to the lymph nodes by expressing CCR7

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26
Q

What do macrophages do in the cell mediated immunity?What do effectorT cells tell macrophages to do?

A

they phagocytose microbes and display the antigens to effector T cellsthe effector t cells tell the macrophage to kill the microbe

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27
Q

What do B cells do in the cell mediated response?

A

they ingest microbes and present them to helper T cells

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28
Q

What cells present antigen to CD8+ (CTL’s)?

A

all nucleated cells

29
Q

How do Naive CD8+ cells react whena virus infects a host cell causing it to not produce the signals needed to initiate T cell activation?What is this process called?

A

using the mechanism wheredendritic cells ingest the infected cells and display theantigens present in the infected cells for recognitionby CD8+ T lymphocytethis is cross-presentation

30
Q

can both, CD8 and CD4 cells use cross presentation mechanism?

A

yes

31
Q

what are MHC molecules?

A

they are membrane proteins in APC’s that display peptide to T cells

32
Q

what is the most important molecule when doing a tissue graft?

A

MHC

33
Q

on what chromosome are the MHC locus?

A

Ch.6

34
Q

What genes are in MHC 2 locus?

A

HLA- DP, DR, DQ

35
Q

What are the genes in the MHC 1 locus?

A

HLA-ABC

36
Q

What are the 2 sets of highly polymorphic genes found in the MHC locus?

A

1) MHC 12) MHC 2

37
Q

how are the MHC locus genes (very characteristic)?

A

highly polymorphic

38
Q

what subunits in the MHC 2 are nonpolymorphic?

A

alpha and beta subunits

39
Q

what does the invariant portion of MHC 1 bind?what is the invariant portion of the MHC 1 molecule?

A

CD8 co-receptorthe alpha 3 domain

40
Q

what does the MHC 1 structure share with the MHC 2 structure?

A

they both have a peptide binding cleft

41
Q

what is different about the globulin composition in MHC 1 and MHC 2?

A

MHC 1 has a beta 2microglobulin and 3 alphasMHC 2 has alpha 1 and 2 bound and beta 1 and beta 2 bound

42
Q

what alpha sub-units in the MHC 1 structure form the peptide binding cleft?

A

alpha 1 and alpha 2

43
Q

what is the invariant chain in the MHC 2 molecule?what does the MHC 2 invariant chain bind to?

A

beta 2 domainbind to the CD4 co-receptor

44
Q

what chains in the MHC 2 molecule form the peptide binding cleft?

A

the alpha 1 and beta 1

45
Q

what domain is nonpolymorphic in the MHC 2 molecule?

A

the beta 2 domain

46
Q

how are the MHC genes expressed?

A

codominantly because they are inherited from both parents

47
Q

What cells express MHC 2?

A

dendritic cells, macrophages, monocytes and B cells

48
Q

what are the 3 polymorphic MHC 1 genes?

A

HLA- A/B/C

49
Q

What are the 3 polymorphic MHC 2 genes?

A

1) HLA-DQ A1, HLA-DQ A22) HLA-DP A1, HLA-DP B13) HLA-DR A1, HLA-DR B1/B2/B3/B4/B5

50
Q

Many peptides arepresented by each MHC molecule?Why? what kind of molecule can the MHC bind?

A

1 because there is only 1 peptide cleft and only bind peptide

51
Q

when do MHC’s get their peptide cargo?

A

during their biosynthesis inside the cell

52
Q

MHC molecules will display peptides from microbes that are found inside host cells, with this in mind, what cell mediates the immunity to intracellular microbes?

A

MHC restricted T cells

53
Q

from where do MHC 1 molecules get their peptide?

A

from cytosolic proteins that get transported to the ER

54
Q

from where do MHC 2 molecules get their peptide?

A

from intracellular vesicles

55
Q

dendritic cells, B cells, and macrophages will put extracelullar proteins that get internalized where?

A

in intracellular vesicles to later be processed

56
Q

how will B cells, dendritic cells, and macrophages internalize extracellular proteins?

A

by having microbe bind to :- receptor specific of microbial product- Fc receptor- products of comlement activation attached to the microbe already (C3b or CR1)

57
Q

what molecules do MHC 2 cells use to transport peptides or load the MHC molecule?

A

Ii or invariant chain

58
Q

what molecules do MHC 1cells use to transport peptides or load the MHC molecule?

A

TAP

59
Q

MHC 2 processing of internalized vesicular antigens

A
  • take up intracelluar peptide and put into a vacuole- then degradedin lysosome; (at the same time the MHC 2 molecule is synthesized in ER and put on an endosome with the cleft boud to CLIP)- CLIP is removed using HLA-DM- the peptide then binds to the MHC 2 molecule- complex is now transported to surface
60
Q

When the newly synthsized MHC 2 molecule does not bind to the broken down peptide, what happens?

A

it is degraded

61
Q

peptide fragments that bind to the MHC molecule are called what?

A

immunodominant epitopes of the antigen

62
Q

What another name for CLIP?

A

Ii, invariant chain

63
Q

class I MHC pathway of processing cytosolic antigen

A
  • virus in cytoplasm makes protein or the protein gets taken up through phagocytosis of the microbe itself- the protein is unfolded in the cytoplasm and ubiquinated, then degraded by proteosome- the peptides produced get transported to the ER by TAP- Peptides get trimmed and bound to newly made MHC 1- MHC 1 bound to peptide gets moved to cell surface
64
Q

how do viruses evade MHC 1 presentation?

A
  1. Removing newly synthesized MHC molecules from the ER2. Inhibiting the transcription of MHC genes3. Blocking peptide transport by TAP
65
Q

What is the consequence of MHC 1 reduction by a virus?

A

CD 8+ (CTL’s) can’t detect these cells to kill the virus

66
Q

What ensures that T cells respond only to cell-associated antigens?

A

the need to recognize the MHC molecule associated with the antigen’s peptide

67
Q

what benefit does it have to segregate between MHC 1 and 2?

A

It allows the ability to respond to intracelullar as well extracellular antigens

68
Q

Who will present antigen taken up from the extracellular environment?What will macrophages do once they have it?

A

Macrophages and B cells (both have MHC 2)macrophages will present it to T helper cells who will activate the macrophage to destroy the microbe and activate B cells to produce antibodies against all other extracellular microbes

69
Q

What happens to microbes that are in the cytoplasm of an infected host? (intracellular microbe)

A

Cytotoxic T cells will eradicate it

Immunology Block 1 (5 decks)

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