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Immunology > Lec5 Antigen Capture and Processing > Flashcards

Lec5 Antigen Capture and Processing Flashcards

1
Q

What form of antigen do T cells recognize?

A

antigen as peptide presented on pAPC with MHC

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2
Q

Do T cells recognize free antigens?

A

No!

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3
Q

What makes pAPC unique?

A
  • express MHC class I AND class II

- only cells capable of activating naive T cells

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4
Q

What is most effective cell at activating naive T cells?

A

Dendritic cell

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5
Q

What are three types of pAPC

A
  • dendritic cells
  • macrophages
  • B cells
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6
Q

Is MHC always on cell surface even in non-infected cells?

A

Yes - with self-protein

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7
Q

What is most polymorphic genetic system known?

A

MHC molecules

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8
Q

2 Reasons for diversity in MHC

A
  • number of different genes

- variety of alleles [alternate forms] for eah gene

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9
Q

Structure of MHC Class I Molecules

A
  • 1 alpha wtih 3 domains: contains binding pocket
  • 1 beta [beta microglobulin
    only one transmembrane region
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10
Q

Structure of MHC Class II Molecules

A
  • 1 alpha with 2 domains
  • 1 Beta with 2 domains
  • binding pocket = a1 and b1
    two transmembrane eregions
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11
Q

What does MHC need to bind cell surface stably?

A

Needs to bind peptide first

If not it will come off before T cell has time to see it

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12
Q

What is DM?

A
  • Intracellular protein involved in peptide presentation by MHC class II
  • in endosomes promotes dissociated of CLIP [place holder peptide] from MHC class II to allow MHC to bind antigen
  • MHC Class II, CD4
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13
Q

What is TAP? What MHC and T cell associated?

A

Transporter associated with antigen processing [TAP]

  • aids in peptide translocation from cytosol into ER in endogenous pathway
  • needed for antigen - MHC class I interaction [CD8]
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14
Q

What cells express MHC Class I? Present cytosolic or external proteins? Present to what type of T cell?

A
  • expressed on most nucleated cells
  • present cytosolic proteins
  • to CD8 T cells
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15
Q

What cells express MHC Class II? Present cytosolic or external proteins? Present to what type of T cell?

A
  • expressed on pAPCs: macrophages, B cells, active T cells
  • present external proteins
  • to CD4 T cells
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16
Q

What is significance of Co-dominant expression of MHC? What does it mean?

A
  • we inherit 3 class I and 3 class II molec from each parent
  • both parental alleles of each MHC are expressed
  • increases number of different MHC molec that can present peptides to T cells
17
Q

What part of MHC is variable? What function does this allow?

A
  • the part in the peptide binding cleft

- allows it to bind different peptides

18
Q

Exogenous pathway of antigen processing? What type of MHC? What type of T cell?

A
  • for pathogens that come from outside of cells
  • ex. extraecllular bacteria
  • uptake extracellular protein and proces in endosome
  • class II MHC molec interact with antigen in endosome
  • peptide-MHC complex expressed on cell surface for CD4 T cells
  • involves CLIP, DM
19
Q

Endogenous pathway of antigen processing? What type of MHC? What type of T cell?

A
  • for pathogens that replicate within cell
  • ex. viruses
  • transport peptides from cytosol to ER
  • assembly MHC class I - peptide complex
  • Express MHC class I and peptide on cell surface to CD8 T cell
20
Q

Endogenous or exogenous for viruses?

A

Endogeneous

21
Q

Are viruses or bacteria process via exogenous pathway?

A

bacteria

22
Q

What is CLIP? Functions with what type of MHC and T cell?

A
  • Class II associated invariant chain peptide
  • binds MHC to prevent binding of self-peptide fragments prior to MHC localization to endosome
  • in presence of antigen peptide, releases MHC to allow MHC to bind
  • CD4
23
Q

What is cross-presentation?

A
  • APC takes up exongeous antigen but antigen goes into cytosol and undergoes endogenous pathway
  • presents MHC Class I to CD8 [CTL]
  • allows presentation of exogenous antigens that are normally presented by MHC II by MHC I

Immunology (17 decks)

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