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Immunology > part 6 > Flashcards

part 6 Flashcards

1
Q

what is the endomembrane system

A

ER, Golgi, transport vesicles, endosomes, lysosomes.

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2
Q

what are the functions of the endomembrane system

A

transportation, storage, degradation, and production

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3
Q

what are clathrin

A

a set of proteins that allow for the formation of the endosome as a pathogen is being taken in.
Found on the surface of the cell.

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4
Q

what is cathepsin

A

Cysteine proteases
S, L, B, D
Need an acidic environment to be activated (acidification).

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5
Q

what are the four types of cathepsin

A

S: almost all APCs express this enzyme
L: expressed in thymic cortisol cells (T cell training in thymus)
B and D: plays a role, but not much.

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6
Q

what pathogens bind to MHC I

A

cytosolic

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7
Q

what pathogens are are presented to CD8 cells

A

cytosolic
cell death

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8
Q

what pathogens are presented on MHC II

A

intravesicular and extracellular

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9
Q

what pathogens are presented to CD4 cells

A

intravesicular and extracellular

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10
Q

how are intravesicular pathogens neutralized

A

activates killing; endocytic vesicles (low pH)

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11
Q

how are extracellular pathogens neautralized

A

presenting cell activates B cells to secrete Ig; endocytic vesicles (low pH)

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12
Q

what are TAPs

A

transports peptides from the cytosol into the endoplasmic reticulum, thereby selecting peptides matching in length and sequence to respective MHC class I molecules

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13
Q

how many TAPs are there

A

1 and 2

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14
Q

how long are the peptides TAP transports

A

8-16 AAs long

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15
Q

what are the physical properties of TAP

A

TAP 1 and 2 transversing the membrane, with ATP binding cassesttes exposed on cytosol side

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16
Q

what is the proteasome complex

A

Tube-like complex
Degradation complex
Takes chains of amino acids and chops them.
Main type of proteasome completely degrades proteins.

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17
Q

what are the parts of the proteasome complex

A

The catalytic chamber (20S Core) is where digestion takes place.
Made up of 7 columns; 4 proteins per column.

Ubiquitin protein: highly-conserved, about 73 amino acids long
Targets proteins for degradation (tagging).

19S regulatory particle of proteasome binds to ubiquitin

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18
Q

what is ubiquitin? why is it important

A

a protein found in most tissues (ubiquitous)
Proteins are marked for degradation by the attachment of ubiquitin to the amino group of the side chain of a lysine residue

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19
Q

what is the immunoproteasome complex for

A

antigen presenting

20
Q

what does interferon secretion upregulate

A

upregulates the amount of MHC I presented on the surface, which allows for upregulation of TAP LMP2 and LMP7, (MECL-1) (core protein)
PA28 (regulatory proteins)

21
Q

what is the first step of MHC I expression

A

Partially folded MHC class I alpha chains bind to calnexin (chaperone protein) until B2-microglobulin binds.

22
Q

what is the second step of MHC I expression

A

MHC class I alpha:beta complex is released from calnexin, binds to chaperone complexes (calreticulin and ERp57) and binds to TAP via tapasin

23
Q

what does tapasin do

A

associates with TAP

24
Q

what is ERp57

A

thioreductase (breaking disulfide bonds)

25
Q

what are DRiPs

A

About 30% of all proteins are defective (DefectiveRibosomalProducts)
DRiPs are chopped up by proteasome

26
Q

what is the third step of MHC I expression

A

Cytosolic proteins and DRiPs are degraded to fragments by proteasome. TAP delivers peptides to ER.

27
Q

what is TRiC

A

protects peptides from being degraded as they move to TAP.

28
Q

what is ERAAP

A

cuts and modify TriC from peptides

29
Q

what is the fourth step of MHC I expression

A

Peptide binds to MHC and the MHC finishes its folding. MHC is released from the TAP complex, is transported, and is expressed on cell membrane.

30
Q

how do viruses evade being destroyed by the immune system

A

by messing with the MHC, TAP, and MHC chaperone complex
Herpes, adenovirus

31
Q

what happens in early endosomes when antigen is first taken in

A

pH is neutral and endosomal proteases are inactive.
Chloroquine prevents acidification of endosomes.

32
Q

what is the first step of MHC II expression

A

Antigen is taken into the cytosol by vesicle

33
Q

what is the second step of MHC II expression

A

Acidification within the vesicle activates proteases to degrade antigen into peptide fragments.

34
Q

what is the third step of MHC II expression

A

Vesicles containing peptides fuse with vesicles containing MHC II molecules, where the MHC II is later expressed on the surface of the cell.

35
Q

what happens to the MHC II vesicle as it moves to the surface of the cell

A

it moves through different vesicles

36
Q

what maintains MHC II when not bound to pathogen proteins

A

bound to invariant protein

37
Q

what is the structure of an invariant protein

A

9 protein complex

38
Q

where is the invariant protein bound on MHC II

A

binds in the groove of MHC II

39
Q

what is the first step of invariant cleaving

A

Ii is cleaved initially to leave only a fragment bound to MHC II and membrane

40
Q

what is the second step of invariant cleaving

A

Ii is further cleaved into CLIP, which is only bound to the MHC II molecule

41
Q

what swaps the invariant with the antigen for MHC II

A

HLA-DM swaps invariant chains with the antigen (peptide editing)

42
Q

what does HLA-DM resemble

A

resembles MHC II with no binding site.

43
Q

where/when is the invariant switched with the antigen

A

MIIC (a compartment) is where HLA-DM swaps CLIP with antigen
During second step

44
Q

what produces more HLA-DM

A

IFN a, b, and g

45
Q

what does HLA-DO do

A

it is an inhibitor to HLA-DM and competitor of HLA-DM

46
Q

when are self-peptides expressed

A

presented on MHC II in order for cell replacement in the periphery
Tolerance

47
Q

what is special about dendritic cells

A

A dendritic cell (swallows cell) can take an antigen presented on MHC and present it on themselves.

Immunology (11 decks)

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