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IMMUNOLOGY > Lecture 9: MHC and Antigen Presentation > Flashcards

Lecture 9: MHC and Antigen Presentation Flashcards

1
Q

term for the generation of peptides from proteins

A

antigen processing

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2
Q

what is antigen presentation

A

display of processed peptide on cell surface via a MHC molecule

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3
Q

what are the 3 types of professional APCs

A
  • DC
  • Macrophages
  • B cells

*carry both MHC class I and II

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4
Q

is antigen presentation exclusive to APCs

A

no

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5
Q

cytosolic pathogens

A

viruses and some bacteria replicate in host cell cytosol

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6
Q

intravesicular pathogens

A

some bacteria can survive and replicate inside of the phagosome

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7
Q

extracellular pathogens

A

bacteria growing outside cell wall, virus not yet in a target cell

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8
Q

what do dendritic cells activate

A

Naive T cells

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9
Q

DCs sample their environment using ?

A

Toll like receptors

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10
Q

MHC molecules only bind _____ peptides

A

linear

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11
Q

what type of peptides do MHC Class I molecules bind? What are they displayed to?

A

endogenous peptides
displays them to CD8+ T cells

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12
Q

what type of peptides do MHC Class II molecules bind? What are they displayed to?

A

exogenous peptides
displays them to CD4+ T cells

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13
Q

what class of MHC is expressed by all nucleated cells

A

Class I

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14
Q

What class of MHC is expressed only by PAPCs

A

Class II

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15
Q

in what part of the cell do peptides bind MHC class I

A

in the ER

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16
Q

what is the role of proteasome?

A

breaks protein chain into small peptides and releases into cytoplasm (proteolysis)

INF-y increased the rate of proteolysis

17
Q

what is the role of transporter proteins (TAP)

A

carry peptides of 8-16 amino acids into the ER

18
Q

what is the role of ERAAP

A

further degrades peptide fragments to ensure they can fit into binding cleft

19
Q

how can viruses evade antigen presentation

A

through the production of proteins called immunoevasins

20
Q

how do immunoevasins
work

A
  • block TAP function
  • block antigenic peptide loading into MHC
  • can tag MHC molecules for degradation by proteosome
21
Q

what do intravesicular proteases do

A

degrade proteins

22
Q

where do MHC Class II molecules form and fold

A

in the ER, then bud off and merge w/ antigen containing vesicle

23
Q

what is the role of an invariant chain

A

it forms a complex w/ MHC class II, blocking the binding of peptides and misfolded proteins

24
Q

what is the role of HLA-DM

A

similar to MHC II
- catalyzes the loading of antigen into MHC II binding pocket

  • found only in MHC class II compartment
25
Q

what is cross-presentation

A

occurs when DCs present antigens on their MHC I molecules that were not generated in their own cytosol

  • rather, they were extracellular pathogens that were processed and displayed on MHC Class I

**critical for the activation of naive CD8 T cells

26
Q

how do MHCs bind to so many antigens

A

genetic diversity

27
Q

what does it mean that MHC molecules are co-dominantly expressed

A

both parental alleles of each MHC gene are expressed

28
Q

what is an HLA haplotype?

A

the set of MHC alleles (class I and II) present on each chromosome

each animal has 2 HLA haplotypes (one from mom/dad)

29
Q

what is the result of each MHC allele being polymorphic and polygenic?

A

each animal expresses a unique combination of MHC molecules

30
Q

why are animals w/ MHC heterozygous alleles at an advantage to MHC homozygous alleles?

A

MHC heterozygous can respond to a greater range of antigens and therefore are best fit to survive infectious disease

31
Q

MHC Class I Loci is encoded by….

A

HLA-A, -B, -C

32
Q

MHC Class II Loci is encoded by….

A

HLA-DP, -DQ, -DR

33
Q

polymorphic MHC means?

A

multiple alleles for each gene

34
Q

give 2 examples of the expression of certain MHC alleles and disease susceptibility

A

Canine rheumatoid arthritis, I-M hemolytic anemia diabetes Mellitus

expression of certain BoLA alleles and resistance to bovine leukosis

35
Q

what are superantigens

A

toxins (either bacterial or viral) that encourage unusual binding of TCR and MHC Class II molecules

binding becomes long-lived and produces a cytokine ‘storm’

36
Q

what does it mean that MHC molecules have broad specificity?

A

many different peptides can bind to the same MHC molecule

however each MHC molecule displays one peptide at a time

37
Q

what class of MHC do cytosolic peptides bind to

A

MHC class I

38
Q

what class of MHC do intravesicular pathogens bind to

A

MHC class II

39
Q

what class of MHC do extracellular pathogens and toxins bind to

A

MHC class II

IMMUNOLOGY (26 decks)

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