Antigen processing and Presentation

Question 1

BCR recognizes

Answer 1

and binds free antigen that is part of a larger pathogen or toxin

Question 2

TCR recognizes

Answer 2

and binds both antigenic peptide and MHC to which peptide is bound
- Protein antigens must be processed into peptide fragments and presented by self-MHC molecules in order to be recognized by TCRs on responding T cells

Question 3

Endogenous antigens

Answer 3

are processed via the cytolytic or endogenous pathway and presented on MHC class 1

Question 4

Exogenous antigens

Answer 4

are processed via the exogenous pathway and presented on MHC class 2 molecules

Question 5

Class 1 presentation

Answer 5

requires cytosolic or endogenous processing

Question 6

Class 2 presentation

Answer 6

requires exogenous processing

Question 7

MHC class 1 molecules interact with peptides derived from

Answer 7

cytosolic degradation of endogenously synthesized proteins

- cytosol

Question 8

MHC class 2 molecules associate with peptides derived from

Answer 8

Endocytic degradation of exogenous antigen

- Endosome/Lysosome

Question 9

The amount or level of each type of protein inside a cell is carefully regulated primarily through?

Answer 9

1. Degrade proteins (proteasome, lysosomes)

2. Translation/ transcription (make more)

Question 10

Peptides that associate with MHC class 1 molecules

Answer 10

are generated by protease complexes called proteasome

Question 11

Proteasome

Answer 11

• recognizes and degrades Ubiquitin tagged proteins

- protease complexes that generate peptides that associate with MHC class 1 molecules

Question 12

Ubiquitin

Answer 12

used to ‘tag’ intracellular proteins for degradation

Question 13

immunoproteasome

Answer 13

cleaves ubiquitinated proteins into fragments that pair better with MHC molecules

Question 14

Endogenous pathway

Answer 14

1. Peptides are transported from the cytosol to the Rough endoplasmic reticulum (RER)
2. TAP molecules in the RER move the fragments
3. MHC class 1 molecules synthesized by ribosomes on the RER anchor in the RER membrane after they translation
4. Chaperone proteins help fold MHC class 1 and put it in close proximity to TAP
5. ERAP trims long peptides to a suitable size for MHC class 1 grooves
6. Endogenous antigen is degraded by an immunoproteasome
7. Peptide is transported to RER via TAP
8. MHC class 1 alpha chain binds calnexin and ERp57, the beta2-microglobulin. Calnexin dissociates. Calreticulin and tapas in bind. MHC captures peptide, chaperones dissociate
9. MHC class 1- peptide is transported from RER to golden complex to plasma membrane

Question 15

Chaperone proteins

Answer 15

• Calnexin
• ERp57
• Calreticulin
• Tapasin
• Help fold MHC class 1 and put it close proximity to TAP

Question 16

ER aminopeptidase (ERAP)

Answer 16

trims long peptides to a suitable size for MHC class 1 grooves

Question 17

Extracellular material can gain access to vehicular components through

Answer 17

• Phagocytosis
• Receptor-mediated endocytosis
• Autophagy

Question 18

Phagocytosis

Answer 18

actin mediate

Question 19

Receptor-mediated endocytosis

Answer 19

• receptor will be recycled
• pH drop
• antigen will be shuttled to lysosome
• how B-cells recycles

Question 20

Autophagy

Answer 20

will be directed toward the lysosome

Question 21

Peptides that associate with MHC class 2 molecules are generated from extracellular antigens in

Answer 21

membrane- bound vesicles

- endosomes

Question 22

Endosomes

Answer 22

are fused with lysosome as an MHC late lysosome which becomes acidic and helps degrade contents

Question 23

Exogenous pathway

Answer 23

• MHC class 2 molecules are produces, associated with invariant chain (Ii) and exported in nestles from ER to Golgi
• Peptides assemble with class 2 MHC molecules in late endosomes

1. The invariant chain (Ii) binds to MHC class 2 alpha and beta chains, blocking endogenous peptides from bindind
2. MHC-Ii complex is routed through Golgi to endocytic pathway compartments
3. Invariant chain is degraded, leaving CLIP fragment
4. Exogenous antigen is taken up, degraded, routed to endocytic pathway compartments
5. HLA-DM mediates exchange of CLIP for antigenic peptide
6. MHC class 2-peptide is transported to palms membrane

Question 24

Invariant chain

Answer 24

• prevents peptide from binding to the groove too early in ER
• uses sorting signals to direct MHC class 2 molecule-containing vesicles to peptide-containing endocytic compartments

Question 25

CLIP

Answer 25

Ii is initially degraded by proteolytic activity within endocytic compartment to class 2-associated invariant chain

Question 26

HLA-DM

Answer 26

exchanges CLIP out of the groove for a peptide

Question 27

How does the immune system activate CD8+ T cells to eliminate intracellular microbes if the APC isn’t infected?

Answer 27

dendritic cells are capable of carrying out cross-presentation

Question 28

Cross-presentation

Answer 28

• exogenous antigens are redirected to the endogenous presentation pathway
• This allows for antigen presentation on MHC class 1 molecules