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Immuno Block 1 > MHC > Flashcards

MHC Flashcards

1
Q

What is the Major Histocompatability Complex?

A

• a large cluster of genes encoding specialized glycoproteins; many functions

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2
Q

What is the most important role of MHC?

A

•• role in antigen presentation to T cells ••

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3
Q

T/F T cells ONLY recognize peptides bound to MHC molecules

A

true

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4
Q

Of the MHC I characteristics, which is the same throughout all individuals

A

B2- microglobulin

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5
Q

Describe peptide binding of MHC

A
  • each MHC molecule (class I or class II) can bind to many different peptides
  • MHC class I and class II molecules do have slightly different peptide-binding characteristics
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6
Q

Describe the binding cleft of MHC class I molecules

A

is closed

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7
Q

Compared to MHC I, the ability of MHC II to bind to peptides is what?

A

less restrictive

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8
Q

the binding cleft of MHC class I molecules is closed and will only bind to peptides with what length of AA?

A

between 8-10 amino acids in length

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9
Q

Peptide binding to MHC I is stabilized how?

A

stabilized by contacts between the aminoterminal and carboxyterminal ends of the peptide and invariant sites found at the ends of the binding grooves

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10
Q

Describe the binding cleft of MHC II

A

the binding cleft of MHC class II molecules is open;

the ends of the peptide can hang over the edge of the cleft

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11
Q

MHC II will bind peptides of what length?

A

will bind to peptides at least 13 amino acids in length, and can be much longer

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12
Q

How is MHC II stabilized?

A

peptide binding is stabilized by contacts between the peptide backbone and conserved residues that line the MHC class II binding groove

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13
Q

MHC Class I Ag-Processing and Presentation Pathway (4 steps)

A
  1. class I HC is stabilized by calnexin until B2-microglobulin binds
  2. calnexin released and heterodimer of class I HC and B2-mg forms peptide-loading complex with clareticulin, tapasin, TAP, ERp57, and PDI
  3. peptide delivered by TAP binds to class I HC, forming mature MHC I molecule
  4. class I molecule dissociates from the peptide-loading complex, and is exported from the ER
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14
Q

What is step 1 of MHC Class I Ag-Processing and Presentation Pathway?

A

class I HC is stabilized by calnexin until B2-microglobulin binds

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15
Q

What is step 2 of MHC Class I Ag-Processing and Presentation Pathway?

A

calnexin released and heterodimer of class I HC and B2-mg forms peptide-loading complex with clareticulin, tapasin, TAP, ERp57, and PDI

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16
Q

What is step 3 of MHC Class I Ag-Processing and Presentation Pathway?

A

peptide delivered by TAP binds to class I HC, forming mature MHC I molecule

17
Q

What is step 4 of MHC Class I Ag-Processing and Presentation Pathway?

A

class I molecule dissociates from the peptide-loading complex, and is exported from the ER

18
Q

Describe the antigen presentation to T cells wrt to MHC I

A
  1. intracellular antigen processing to peptides in proteasome
  2. peptide transport into ER
  3. peptide binding by MHC I
  4. MHC I presents peptide at cell surface
19
Q

Describe the MHC Class II Ag-Processing and Presentation Pathway (4 steps)

A
  1. invariant chain blocks binding of peptides to MHC II molecules in ER
  2. in vesicles invariant chain is cleaved, leaving the CLIP fragment bound
  3. CLIP blocks binding of peptides to MHC II in vesicles
  4. HLA-DM facilitates release of CLIP, allowing peptides to bind
20
Q

What is step 1 of MHC Class II Ag-Processing and Presentation Pathway?

A

invariant chain blocks binding of peptides to MHC II molecules in ER

21
Q

What is step 2 of MHC Class II Ag-Processing and Presentation Pathway?

A

in vesicles invariant chain is cleaved, leaving the CLIP fragment bound

22
Q

What is step 3 of MHC Class II Ag-Processing and Presentation Pathway?

A

CLIP blocks binding of peptides to MHC II in vesicles

23
Q

What is step 4 of MHC Class II Ag-Processing and Presentation Pathway?

A

HLA-DM facilitates release of CLIP, allowing peptides to bind

24
Q

describe Antigen Presentation to T Cells wrt to MHC class II

A
  1. extracellular antigen endocytosed
  2. peptide production in phagolysosome
  3. peptide binding by MHC II
  4. MHC II presents peptide at cell surface
25
Q

Describe how MHC molecules present peptides to T cells

A

CD4 T cells recognize peptides bound to MHC class II

CD8 T cells recognize peptides bound to MHC class I

26
Q

What is the Significance of MHC Distribution? (2)

A
  • MHC molecules present peptides to T cells
  • immune response is “tailored” to the type of infection
27
Q

Describe how immune response is “tailored” to the type of infection

A

Ab-mediated immune responses best for clearance of extracellular pathogens

T cell-mediated immune responses are best for clearance of intracellular pathogens

28
Q

What is the existence in the genome of several different genetic loci encoding structurally similar proteins of identical function (isoforms)?

A

polygeny

29
Q

What is the existence of two or more forms (alleles) of a given gene within the population (variant alleles occur at a frequency of at least 1%)?

A

Polymorphism (genetic)

30
Q

Describe the genes MHC I inherited

A

3 MHC class I gene on each chromosome

  • HLA-A
  • HLA-B
  • HLA-C
31
Q

Describe the genes MHC II inherited

A

each person inherits at least 3 MHC class II genes on each chromosome

  • HLA-DP
  • HLA-DQ
  • HLA-DR (either 1 or 2 on each chromosome)
32
Q

T/F MHC expression is what?

A

polygenic

33
Q

Describe the minimum number of MHC molecules expressed/person (both classes)

A

3 different MHC class I molecules

3 different MHC class II molecules

34
Q

What is • maximum number of MHC molecules expressed/person? (both classes)

A

6 different MHC class I molecules

48 different MHC class II molecules

35
Q

any tissue bearing non-self MHC will be rejected. Why?

A

T cell-mediated immune response

MHC in Transplant Rejection

36
Q

What is a transplant between genetically identical individuals?

A

syngeneic transplant (isograft)

37
Q

What is a transplant between genetically different individuals?

A

allogeneic transplant (allograft)

38
Q

What is a transplant of tissue from a different species?

A

zenograft

39
Q

Describe what is necessary before a bone marrow transplant and what occurs after

A

bone marrow transplant: host immune system is destroyed prior to transplant

following transplant, mature T cells (from transplant) attack allogeneic tissue of the host

Immuno Block 1 (14 decks)

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