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Host Response > Lecture 8: Major Histocompatibility Complex > Flashcards

Lecture 8: Major Histocompatibility Complex Flashcards

1
Q

T cells only recognize antigens displayed by ______

A

MHC complexes on cell surfaces

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2
Q

alpha:beta cells recognize antigens as _______

A

peptide:MHC complexes

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3
Q

What to MAIT cells and y: gamma cells recognize?

A

different types of surface molecules whose expression may indicate infection or cellular stress.

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4
Q

What can peptide:MHC complexes signal?

A

the presence of an intracellular pathogen for elimination by armed effector T cells

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5
Q

What happens in dendritic cells?

A

peptide:MHC complexes serve to activate antigen specific effector T cells

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6
Q

What does the structure of the TCR/peptide/MHC complexes look like?

A

APC > MHC> Antigen> Variable Regions on the end with J alpha and Beta chains in the middle> then connected to the C alpha and beta region> then going to the T cell

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7
Q

T Cell receptors recognize antigens in the form of________

A

a foreign peptide bound to an MHC molecule.

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8
Q

What is the Structure of MHC 1:

A

-3 alpha chains: 2 on the left, 1 on the right which sits above the B2 microglobulin

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9
Q

What does MHC 2 structure look like?

A

2 beta chains on the left and 2 alpha chains on the left.

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10
Q

What are the four noncovalent forces involved with MHC?

A
  1. Electrostatic Forces
  2. Hydren Bonds
  3. Van der Waals forces
  4. Hydrophobic forces
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11
Q

What are the differences between the distinct subunit compositions of MHC1 and MHC2

A

MHC1: alpha subunits and closed clefts, ranges from 8-10 amino acids, epitopes in antigen are smaller

MHC2: clefts are open so they are longer peptides

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12
Q

MHC 1 binds ______ by both_____

A

short peptides 8-10 amino acids, both ends

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13
Q

Peptides bind to MHC molecules through_____

A

structurally related anchor residues

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14
Q

What is the point of the anchor residues?

A

They allow for peptide binding stability and specificity of the peptide binding

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15
Q

The length of the peptides bound by MHC Class 2 are ______

A

not constrained, meaning it is much longer

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16
Q

Peptides that bind MHC class2 molecules are _______ and their anchor residues lie at _________ from the ends of _____

A

variable in length, various distances, peptides

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17
Q

MHC 2’s variability in length is referred to as ______

A

open hanging characteristics
- not in the pocket but still involved with receptor interactions

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18
Q

What is unique about the dendritic cell?

A

It is a supercell and is uber presenting

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19
Q

Cells become targets of T-cell recognition by ______

A

acquiring antigens from either the cytosolic or the vesicular compartments

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20
Q

Cytosolic Pathogens:

A

Degrades in: cytosol
Peptides bind to: MHC class 1
Presented to: effector CD8 T cells
Effect on presenting cell: cell death

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21
Q

Intravesicular pathogens:

A

Degrades: endocytic vesicles (low pH)
Peptides bind to: MHC class II
Presented to: Effector CD4 T cells
Effect on presenting cell: activation to kill intravesicular bacteria and parasites

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22
Q

Extracellular pathogens and toxins:

A

Degraded in: endocytic vesicles (low pH)
Peptides bind to: MHC Class II
Presented to: Effector CD4 T cells
Effect on presenting cell: activation of B cells to secrete Ig to eliminate extracellular bacteria/toxins

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23
Q

Newly synthesized MHC 1 molecules are retained in _________ until they bind a peptide

A

the endoplasmic reticulum

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24
Q

How is MHC able to exit the ER and go to the cell membrane?

  1. Partly fold MHC class I alpha chains bind to __________
A

calnexin until B2 microglobulins binds

25
Q

How is MHC able to exit the ER and go to the cell membrane?

  1. MHC class 1____ complex is released from calnexin, binds a complex of _______ and binds to TAP via tapasin
A

alpha:b2M complex, chaperone proteins

26
Q
  1. Cytosolic proteins and defective ribosomal products are ________ by the proteasome. TAP delivers _______
A

degraded to peptide fragments, peptides to the ER.

27
Q
  1. A peptide binds the MHC class 1 molecules and completes its ______. The MHC Class 1 molecules is released from _______ and exported to ______
A

folding, the TAP complex, the cell membrane

28
Q

Peptides that bind to MHC II molecules are generated in __________

A

acidified endocytic vesicles

29
Q

Step 1 of MHC2 generation:
1. Antigen is taken up from _______ to _______

A

extracellular spaces into intracellular vesicles

30
Q

Step 2 of MHC generation:
2. In early endosomes of neutral pH, endosomal ________

A

proteases are inactive

31
Q

Step 3 of MHC generation:
3.______ of vesicles actives proteases to degrade antigen into _______ peptide fragments

A

Acidification, peptide fragments

32
Q

Step 4 of MHC generation:
4. Vesicles containing _____ fuse with vesicles containing ______

A

peptides, MHC class 2 molecules

33
Q

The invariant chain is ______ CLIP bound to the MHC class II molecules

A

cleaved to leave a peptide fragment

34
Q

Cleavage steps of invariate chain
1. invariant chain (Ii) binds in the ______ of MHC II molecules

A

grooves

35
Q
  1. II is cleaved initially to leave a fragment bound to the ___________
A

class II molecule and to the membrane

36
Q

Further cleavage leaves a short peptide fragment, _____ to the class II molecules

A

CLIP

37
Q

MHC Class II molecules are loaded with _________

A

peptide in a late endosomal compartment

38
Q

LAMP______

A

not in the lysosyme and upregulated

39
Q

What does an Adaptor Proteins do?

A

vesicle formation, cargo selection and sorting

40
Q

Many ______involved in antigen processing and presentation are encoded by _____within the MHC

A

proteins, genes

41
Q

The protein products of MHC Class I and class II genes are ____________

A

highly polymorphic

42
Q

MHC polymorphism extends the _________ to which the immune system can reponsd

A

range of antigens: polymorphism, polygeny,

43
Q

MHC polymorphism affects __________ by T cells influencing both _______and the contacts between _________

A

antigen recognition, peptide binding, t-cell receptor and MHC molecule

44
Q

The ______ structures of several peptide:MHC:T-cell receptor complexes show a similar orientation of the T cell-receptor over the ________

A

crystal, peptide:MHC complex

45
Q

Why is there a huge variety of HLA?

A

They can group together on an internal chain and bind to specific peptides.

46
Q

MHC polymorphism affects ______ by T cells by influencing both peptide binding and the contacts between T_____

A

antigen recognition, T-cell receptor and MHC molecule

47
Q

Alloreactive cells recognizing _______ are very abundant

A

non-self MHC

48
Q

The CD4 and CD8 cell-surface proteins of T cells are required to ______________

A

make an effective response to antigen

49
Q

MHC Class 2 has a ______ interaction with Cd4

A

beta chain

50
Q

MHC class 1 has a ______ interaction with CD8

A

alpha chain

51
Q

The _____ family of MHC class 1-like molecules is encoded outside the ______ and presents microbial lipids to ________

A

CD1, MHC, CD1-restricted T cells

52
Q

The CD1 family of MHC class 1-like molecules is encoded outside ______ and presents microbial lipids to _________

A

the MHC
CD1-restricted T cells

53
Q

Which MHC class molecule is more restricted?

A

MHC2

54
Q

Dendritic cells are expressed on which classes?

A

both MHC1 and MHC2

55
Q

B cells are expressed on which classes?

A

MHC class 1 and 2

56
Q

T cells are expressed more on ____

A

MHC class 1

57
Q

Neutrophils are expressed on _____

A

MHC class 1

58
Q

What other nucleated cells are expressed on MHC class 1

A

hepatocytes, kidney, and brain

59
Q
A

Host Response (6 decks)

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