Lecture 9: MHC and Antigen Presentation

Question 1

term for the generation of peptides from proteins

Answer 1

antigen processing

Question 2

what is antigen presentation

Answer 2

display of processed peptide on cell surface via a MHC molecule

Question 3

what are the 3 types of professional APCs

Answer 3

• DC
• Macrophages
• B cells

*carry both MHC class I and II

Question 4

is antigen presentation exclusive to APCs

Answer 4

no

Question 5

cytosolic pathogens

Answer 5

viruses and some bacteria replicate in host cell cytosol

Question 6

intravesicular pathogens

Answer 6

some bacteria can survive and replicate inside of the phagosome

Question 7

extracellular pathogens

Answer 7

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

Question 8

what do dendritic cells activate

Answer 8

Naive T cells

Question 9

DCs sample their environment using ?

Answer 9

Toll like receptors

Question 10

MHC molecules only bind _____ peptides

Answer 10

linear

Question 11

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

Answer 11

endogenous peptides
displays them to CD8+ T cells

Question 12

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

Answer 12

exogenous peptides
displays them to CD4+ T cells

Question 13

what class of MHC is expressed by all nucleated cells

Answer 13

Class I

Question 14

What class of MHC is expressed only by PAPCs

Answer 14

Class II

Question 15

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

Answer 15

in the ER

Question 16

what is the role of proteasome?

Answer 16

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

INF-y increased the rate of proteolysis

Question 17

what is the role of transporter proteins (TAP)

Answer 17

carry peptides of 8-16 amino acids into the ER

Question 18

what is the role of ERAAP

Answer 18

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

Question 19

how can viruses evade antigen presentation

Answer 19

through the production of proteins called immunoevasins

Question 20

how do immunoevasins
work

Answer 20

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

Question 21

what do intravesicular proteases do

Answer 21

degrade proteins

Question 22

where do MHC Class II molecules form and fold

Answer 22

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

Question 23

what is the role of an invariant chain

Answer 23

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

Question 24

what is the role of HLA-DM

Answer 24

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

• found only in MHC class II compartment

Question 25

what is cross-presentation

Answer 25

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

Question 26

how do MHCs bind to so many antigens

Answer 26

genetic diversity

Question 27

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

Answer 27

both parental alleles of each MHC gene are expressed

Question 28

what is an HLA haplotype?

Answer 28

the set of MHC alleles (class I and II) present on each chromosome each animal has 2 HLA haplotypes (one from mom/dad)

Question 29

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

Answer 29

each animal expresses a unique combination of MHC molecules

Question 30

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

Answer 30

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

Question 31

MHC Class I Loci is encoded by....

Answer 31

HLA-A, -B, -C

Question 32

MHC Class II Loci is encoded by....

Answer 32

HLA-DP, -DQ, -DR

Question 33

polymorphic MHC means?

Answer 33

multiple alleles for each gene

Question 34

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

Answer 34

Canine rheumatoid arthritis, I-M hemolytic anemia diabetes Mellitus expression of certain BoLA alleles and resistance to bovine leukosis

Question 35

what are superantigens

Answer 35

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'

Question 36

what does it mean that MHC molecules have broad specificity?

Answer 36

many different peptides can bind to the same MHC molecule however each MHC molecule displays one peptide at a time

Question 37

what class of MHC do cytosolic peptides bind to

Answer 37

MHC class I

Question 38

what class of MHC do intravesicular pathogens bind to

Answer 38

MHC class II

Question 39

what class of MHC do extracellular pathogens and toxins bind to

Answer 39

MHC class II