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MDSC 321 > Final MHC > Flashcards

Final MHC Flashcards

1
Q

What are and what do MHC molecules do?

A
  • they display antigens to T cells

- cell surface glycoproteins

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2
Q

How many classes of MHC are there

A

3

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3
Q

What is special about MHC genes?

A

Polygenic, multiple genes for the class (1, 2, 3)

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4
Q

Which chromosome is the MHC gene complex for humans and mice?

A
  • 6

- 17

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5
Q

Explain class 1 MHC?

A
  • present altered self antigens or viruses to activate cytotoxic T cells
  • found on nearly all nucleated cells of the body
  • each gene encodes an alpha chain protein
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6
Q

Explain Class 2 MHC?

A
  • present processed extracellular bacteria to helper T cells
  • expressed only on membranes of antigen presenting cells (macrophage, dendritic cells, B cells)
  • each region encodes both an alpha and beta chain
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7
Q

Within a population is there a lot or a bit of MHC diversity?

A

-a lot of diversity between species

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8
Q

For individuals, is there diversity in MHC?

A

No, all MHC molecules in individuals are the same

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9
Q

Where does the diversity for MHC come from?

A

Polymorphism, multiple alleles within the MHC gene loci

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10
Q

How many MHC 1 and 2 alleles do you inherit from mom and dad

A
  • 3 MHC 1 from mom an 3 from dad

- 3 MHC 2 from mom and 3 from dad

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11
Q

How many MHC 1’s are expressed?

A

All 6 on a nucleated cell

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12
Q

How many MHC’s are expressed on APC’s?

A

12 MHC’s

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13
Q

Describe MHC 1 peptide bonding?

A
  • can only hold a peptide of 8-10 amino acids

- anchor residues hold peptide in place

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14
Q

Describe MHC 2 peptide bonding

A
  • can hold a peptide of 13-18 amino acids
  • peptide is exposed and flat across the surface
  • anchor points distributed across ends and centre of peptide
  • interaction involves hydrophobic residues
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15
Q

What is antigen processing?

A

The degradation of antigens into peptides

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16
Q

What is antigen presentation?

A

Describes the binding of the peptide by MHC and displaying the peptide at the cell surface to interact with T cells

17
Q

Where are MHC 1 antigens processed?

A

In the cytoplasm

18
Q

Where are MHC 2 antigens processed?

A

In the endocytic pathway

19
Q

What is the purpose of antigen processing?

A

To generate peptides that will fit in the MHC binding cleft

20
Q

What are the steps of MHC 1 antigen processing?

A
  1. identification and cleavage of target proteins
  2. transport to endoplasmic reticulum
  3. loading onto MHC 1
  4. expression on cell surface
21
Q

1, 2. Describe identification and cleavage of target proteins and the transport for MHC 1?

A
  • proteins are degraded by proteasomes
  • peptides are then transported from the cytoplasm to the endoplasmic reticulum by the transporter of antigenic peptides (TAP)
22
Q

3, 4. Describe the loading and expression of MHC 1?

A
  • peptides are loaded onto pre-formed MHC 1
  • stabilized by chaperone proteins
  • once a peptide is loaded the chaperone is released
  • the MHC 1 travels in vesicles to the cell surface
23
Q

What are the steps for MHC 2 antigen processing?

A
  1. internalization of target molecules
  2. digestion
  3. synthesis of MHC 2
  4. co-localization of MHC and antigen compartments
  5. peptide loading
  6. transport to cell surface
24
Q

Describe 1. antigen internalization for MHC 2 (4)

A
  • extracellular proteins are internalized via phagocytosis or endocytosis
  • macrophages: phagocytosis
  • B-cells: endocytosis
  • peptides are held in phagosomes or endosomes
25
Q

Describe 2. peptide generation for MHC 2 (5)

A
  • antigen is degraded with the endocytic pathway
  • early endosome
  • late endosomes
  • lysosomes
  • peptides are degraded to 13-18 amino acids
26
Q

Describe 3.Synthesis of MHC 2 (1)

A

-in the endoplasmic reticulum they’re stabilized with chaperone proteins

27
Q

Describe 4.Co-localization for MHC 2 (1)

A

Vesicles containing newly-synthesized MHC 2 travel from the ER, through the golgi and eventually fuse with endolysomes

28
Q

Describe 5.Peptide loading MHC 2 (1)

A

-chaperone protein is degraded and replaced by peptide fragments

29
Q

Describe 6. Surface expression MHC 2 (2)

A
  • once loaded the MHC 2 travels to the cell surface

- fusion of vesicle with the cytoplasmic membrane leads to expression of loaded MHC 2 on the cell surface

MDSC 321 (21 decks)

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