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Immunology > Chapter Six > Flashcards

Chapter Six Flashcards

1
Q

What happens in almost all cells?

A

peptide:MHC complexes can signal the presence of an intracellular pathogen for elimination by armed effected T cells

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2
Q

What happens in dendritic cells?

A

(may not themselves be infected) peptide:MHC complexes serve to activate antigen-specific effector T cells

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3
Q

What is MHC polymorphism?

A

many variants present in population. also has genes involved in processing of antigens to produce peptide:MHC complexes

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4
Q

MHC class one molecules bind

A

peptide recognized by CD8 T cells.

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5
Q

MHC class two molecules bind

A

peptides recognized by CD4 T cells.

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6
Q

What do CD4 and CD8 do?

A

directly contact MHC molecules and are required to make an effective response to antigen

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7
Q

What is antigen processing?

A

generation of peptides from native proteins

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8
Q

What is antigen presentation?

A

peptide display at cell surface by MHC molecules

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9
Q

2 purposes of processing and presenting pathogen derived antigens?

A
  1. inducing dev of armed effector T cells 2. triggering effector functions of these armed cells at sites of infections
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10
Q

What is the cytosol?

A

intracellular compartment which communicates w/ the nucleus via pore in the nuc membrane

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11
Q

What is the vesicular system?

A

comprises the ER, golgi apparatus, endosomes, lysosomes, and other intracellular vesicles

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12
Q

How do cells become targets of T cell recognition?

A

acquiring antigens from either the cytosolic or vesicular compartments

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13
Q

Describe peptide formation.

A

from ubigquitinated proteins in the cytosol by the proteasome: 20S catalytic core & 2 19S regulatory caps

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14
Q

What are the proteolytic subunits?

A

beta-1, beta-2, beta-5 which form the catalytic chamber

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15
Q

What is proteostasis?

A

protein quality control and homeostasis

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16
Q

What is the ubiquitin proteasome system (UPS)?

A

one mechanism for maintaining proteostasis

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17
Q

What determines the function of a peptide?

A

ubiquitin linkage

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18
Q

What is a constitutive proteasome?

A

present in all cells: beta-1, beta-2, beta-5 subunits

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19
Q

What is an immunoproteasome?

A

when involved cells are infected -> more protease activity. induced subunits are β1i (or LMP2), β2i (or MECL-1), and β5i (or LMP7)

20
Q

What does Interferon-γ do?

A

further increases production of antigenic peptides by inducing expression of PA28 proteasome-activator complex that binds to proteasome (binds to either end)

21
Q

What are defective ribosomal products (DRiPs)?

A

peptides translated from introns in improperly spliced mRNAs, translation of frameshifts, etc tagged by ubq for rapid degradition by proteasome

22
Q

Why are DRiPs important?

A

ensures both self-proteins and proteins from pathogens generate abundant peptide substrates for eventual presentation by MHC class I proteins

23
Q

What happens to peptides before they bind to MHC class I molecules?

A

transported by TAP into the ER and are further processed

24
Q

Where do newly synthesized MHC class I molecules stay?

A

ER until they bind a peptide

25
Q

What are the components of the MHC class I peptide-loading complex?

A

chaperones calreticulin, ERp57, tapasin

26
Q

What is “cross presentation?”

A

used by dendritic cells to present exogenous proteins, extracellular antigens (phagocytosis) on MHC class I molecules to prime CD8 T cells

27
Q

How are peptide:MHC class II complexes generated?

A

in acidified endocytic vesicles from proteins obtained through endocytosis, phagocytosis, and autophagy

28
Q

What are acidified endocytic vesicles used for?

A

use to break down pathogens that reside in membrane-enclosed vesicles and make peptides that bind to MHC class II molecules

29
Q

Why is II (invariant chain important)?

A
  1. brings new MHC class II molecule to acidified intracellular vesicles & binds to grove on MHC class II molecule 2. cleaved and puts CLIP in as a placeholder
30
Q

What do MHC class-II like molecules HLA-DM and HLA-DO regulate?

A

exchange of CLIP for other peptides

31
Q

When is MARCH-1 shut down?

A

during infection to increase lifetime of MHC molecules

32
Q

When is MARCH-1 active?

A

innactive dendritic cells to degrade MHC molecules

33
Q

Why can’t pathogens just mutate to avoid presentation by MHC molecules?

A
  1. MHC is polygenic (different MHC class I & II genes) 2. MHC is highly polymorphic (multiple variants of each gene)
34
Q

What does MHC encode?

A

many proteins involved in antigen processing & presentation

35
Q

Where is MHC in humans? What are these gene called?

A

chr. 6 called human leukocyte antigen (HLA)

36
Q

What is MHC in mice called?

A

H-2 genes

37
Q

What is MHC haplotype?

A

particular combo of MHC alleles found on single chromosome

38
Q

What does expression of MHC alleles being codominant mean?

A

protein products of both alleles at a locus are expressed equally in the cell, and other gene products can present antigens to T cells

39
Q

How does MHC polymorphism affect antigen recognition by T cells?

A
  1. peptide binding (main source of allelic variation) 2. contacts between TCR and MHC molecules
40
Q

What is MHC restriction?

A

co-recognition of foreign peptide and MHC molecule bc particular MHC allele product is said to restrict ability of T cell to recognize antigen

41
Q

What does antigen specific TCR recognize?

A

complex consisting of an “antigenic peptide” and a “self MHC molecule”

42
Q

What are superantigens?

A

bind directly to TCRs and to MHC molecules

43
Q

What are MHC class 1b genes?

A

class I region of MHC These genes

44
Q

What is true about the CD1 family of MHC class I-like molecules?

A

CD1a, CD1b, CD1c. bind various microbial glycolipids

45
Q

Group 2 CD1 molecules

A

CD1d: bind mainly self lipid antigens such as sphingolipids and diacylglycerols CD1e is considered intermediate

46
Q

What are iNKT cells (invariant NKT)?

A

CD1-restricted T cells. less diverse using the same TCR-alpha chain but also express NK-cell receptors

Immunology (8 decks)

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