Lecture # 13 Antigen Processing and Presentation - Class II Flashcards Preview

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Flashcards in Lecture # 13 Antigen Processing and Presentation - Class II Deck (22):
1

Exception to endogenous processing

cross presentation allows specialized DCs to endocytose virally infect cells and present via class I to naive CD8 cells.

2

How does cross presentation enable exogenous proteins to be presented by Class I?

1) phagosome ER 2) retrotranslocation through Sec61-ER to cytosol 3) Fusion of ER and phagosome ; important for Naive CD8 T cells

3

How does interferon gamma effect the functionality of the proteosome?

interfereon gamma induces the immunoproteosome from the constitutive proteosome by the replacement of the beta subunit with LMP2, LMP1, MECL-1.

4

What type of pathogens are taken up by Class II pathway?

Bacterial, parasitic, fungal;

5

What cells are involved in the uptake of Class II pathogens?

DCs, macrophages, B Cells and other APCs; secrete cytokines

6

Class II presentation pathway

1) uptake of intracellular proteins 2) processing of uptaken proteins in the endosomal/lysosomal vesicles 3) Transport of MHC II molecules to endosomes 4) Association with Class II MHC molecules in vesicles 5) Expression

7

What is the endosomal protease involved with degradation of pathogens?

Cathepsins (Cathepsin L proteolytic cleavage) (Cathepsin S CLIP processing)

8

Invariant chain

binds to nascent class II to fill the peptide binding groove-stabilizes

9

HLA-DM

helps catalyze the removal of CLIP and addition of processed peptides.

10

Why is invariant chain important?

Invariant chain prevents premature binding of peptides to Class II; binds to alpha and beta chains w/clip

11

CLIP

Class II associated invariant chain peptide prevents other peptides from binding class II.

12

What enzyme cleaves Invariant chain?

Cathepsin S

13

What does HLA-DM do specifically?

mediates the removal of invariant chain, also catalyzes the exchange of CLIP with processed peptides; also catalyzes the release of unstably bound peptides from class II molecule;

14

Exceptions to Class II rule

Autophagy; virally produced proteins in the cytosol gets shuttled into the lysosomes to be loaded on Class II molecules

15

• Autophagy

the normal process of protein turnover and can be enhanced by cellular stressors—starvation—cell must catabolize intracellular proteins to provide energy

16

Micro-autophagy

cytosol is continually internalized into the vesicular system by lysosomal invaginations

17

Macro-autophagy

induced by starvation, double membraned autophagosome engulfs the cytosol and fuses with lysosomes

18

CMA

chaperone mediated autophagy uses heat shock cognate protein 70 and LAMP-2 to transport cytosolic proteins to lysosomes

19

Where do peptides come from (what source) that bind to Class I?

Peptides come from the cytosol. Endogenous. Class I is typically viral.

20

What can increase proteosome function?

Interferon gamma induces the immunoprotesome via PA28. LMP2, LMP7, MECL-1 replaces the beta subunit.

21

What is the Function of TAP?

Transports peptides into the ER lumen

22

List the chaperone proteins associated with Class I

2) ERP57* 3) Calnexin* 5) Calreticulin* *-stabilizes 4) Tapasin- binds to TAP and peptide complex.

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