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LECOM Microbiology MS1 > MHC (Exam 1) > Flashcards

MHC (Exam 1) Flashcards

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1
Q

What is the term for MHC in humans

A

HLA

human lymphocyte antigens

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2
Q

How does MHC play a role in susceptibility to disease and autoimmunity

A

MHC expressed by an individual partly determines their response to an antigen

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3
Q

What is the nomenclature for class 1 HLA

A

A B C

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4
Q

Where will class 1 HLA bind

A

cytotoxic T cells

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5
Q

What is the nomenclature for class 2 HLA

A

Dp, Dq, Dr

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6
Q

Where will class 2 HLA bind

A

Th cells

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7
Q

What chromosomes are all 3 classes of HLA found on

A

6

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8
Q

What class of HLA is nonclassical

A

class 3

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9
Q

What is the gene expression of HLA

A

codominant

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10
Q

What does it mean that the gene expression is codominant

A

both parental copies expressed together

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11
Q

What is the main function of HLA

A

bind antigenic peptides and present them to T cells

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12
Q

What type of antigens do HLA class 1 present and what cell do they present to

A

endogenous (viral) antigens

Tc cells

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13
Q

What type of antigens do HLA class 2 present and what cell do they present to

A

exogenous (bacterial) antigens

Th cells

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14
Q

What will happen if a T cell cannot recognize MHC

A

will die in the thymus

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15
Q

Where is class 1 HLA expressed

A

every nucleated cell

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16
Q

What is class 1 HLA composed of

A

3 alpha chains and a beta 2 microglobulin

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17
Q

What does Class 1 HLA bind

A

short peptides approximately 8-10 aa in length

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18
Q

Where does the antigen bind on class I HLA

A

A1-A2 domains in its cleft

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19
Q

What allows for the highly polymorphic nature of Class 1 HLA

A

several different alleles

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20
Q

What is the function of beta 2 microglobulin in class 1 HLA

A

required for proper folding

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21
Q

Without Beta 2 microglobulin what occurs

A

no class 1 expression, protein folds over on itself and doesn’t bind to proteins

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22
Q

Where are class 2 HLA expressed

A

antigen presenting cells

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23
Q

What are the antigen presenting cells that express class 2 HLA

A

macrophages
B cells
dendritic cells

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24
Q

Do macrophages, B cells, and dendritic cells have class 1 HLA

A

yes. they are nucleated

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25
Q

What are class 2 HLA composed of

A

an alpha and a beta chain

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26
Q

How big are the peptides that bind to class 2 HLA

A

12-15aa in length

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27
Q

Where does antigen bind to class 2 HLA

A

cleft between alpha 1 and beta 1 chains

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28
Q

What alleles are many autoimmune diseases associated with

A

Dr

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29
Q

What is the water affinity for the transmembrane regions of class 1 and 2 HLA

A

hydrophobic

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30
Q

What is antigen processing

A

process by which peptides get loaded into the HLA and presented to Tc or Th cells

31
Q

What are the two different types of peptides in antigens

A

endogenous

exogenous

32
Q

Where do endogenous peptides bind

A

class I HLA

33
Q

Where do exogenous peptides bine

A

class II HLA

34
Q

What is the function of proteosomes

A

degrade larger viral proteins into small peptides

35
Q

HLA molecules are in the ER and peptides are in the cytoplasm how do the HLA molecules get loaded

A

Tap 1 and Tap 2

36
Q

What does TAP stand for

A

Transporter for Antigen processing

37
Q

What is Tap

A

molecular tunnel that shuttles peptides from cytoplasm into the ER

38
Q

HLA class 1 antigen are in the ER. How do they make it to the cell surface to present to Tc cells

A

vesicular transport through the golgi to the surface

39
Q

What type of protein will enter a proteosome

A

ubiquitinated protein

40
Q

What is essential to keep class I MHC folded properly

A

chaperones and peptides within the binding groove

41
Q

What two things are required in order for endogenous antigen to be presented

A

TAP and B2

42
Q

What is the process by which Class 1 MHC will present endogenous antigen

A

ubiquinated protein sent to proteosome where it will be degraded. Peptides sent through TAP to the ER

Peptides replace self antigen on class I MHC. MHC with antigen goes through vesicular transport to be expressed on cell surface

43
Q

What will be seen with TAP deficiency

A

class 1 MHC deficiency. Susceptible to viral infections

44
Q

What will class 1 MHC present in an infected and healthy individual to cause an immune response

A

infected: viral antigen
healthy: self antigen

45
Q

Why can’t class 2 MHC bind peptides in the ER

A

because it is bound to an invariant chain

46
Q

What is the function of the invariant chain in exogenous antigen processing

A

prevents the binding of endogenous antigen. Ensures that only class 1 will present endogenous antigens

47
Q

What is the function of HLA-DM

A

pulls out the clip to free up peptide binding groove for the antigen

48
Q

Describe the process in which class 2 MHC will express exogenous antigen

A

vesicle with class 2 MHC with its invariant chain will fuse with a phagolysosome

Acid chews up most of the invariant chain leaving a CLIP piece in place

CLIP has higher affinity for HLA-DM and will bind to HLA-DM leaving a free peptide groove for antigen to bind

Fuses to cytoplasmic membrane

49
Q

What class of MHC will APCs express

A

both class 1 and class 2

50
Q

What is the purpose of cross priming

A

puts Th and Tc cells in closer proximity allowing Tc cells to become stronger killers due to access of cytokines from Th cells

51
Q

What is the process of cross-priming

A

dendritic cell will engulf the entire viral infected cell: presents the viral antigen on class 1 MHC and both class 2 MHC.

Th recognizes class 2 MHC and releases IL-2 which will act on Tc to make it a better killer

52
Q

On what type of cell will cross priming occur

A

dendritic cells

53
Q

Which HLA class is more suscpetible to disease

A

class 2

54
Q

What type of HLA deficiency would be more severe

A

class 2 as the entire immune response would be lost as you cannot present to Th cells

55
Q

What is the factor that can increase the risk of diseases associated with HLA

A

inbreeding

56
Q

How does inbreeding affect HLA

A

reduces heterogeneity in HLA type causing diseases to be more prevalent in these populations

57
Q

What can IFN gamma and TNF increase expression of

A

class 2 MHC

58
Q

How can IFN gamma and TNF increases expression of class 2 MHC

A

induces the formation of specific transcription factors that bind to promotors of MHC genes

59
Q

What affect can CMV proteins have on MHC class 1 complex

A

binds to beta 2 microglobulin preventing the proper assembly of class 1 mhc

60
Q

How might viruses affect the expression of MHC and how is this combatted

A

mask expression of MHC

combatted by NK cells

61
Q

What are the names of MHC class 1

A

HLA-A
HLA-B
HLA-C

62
Q

What are the names of MHC class 2

A

HLA-DP
HLA-DQ
HLA-DR

63
Q

Where are MHC class 1 found

A

all nucleated cells

64
Q

Where are MHC class 2 found

A

antigen presenting cells

65
Q

What recognizes MHC class 1

A

CD8 cells

66
Q

What recognizes MHC class 2

A

CD4 cells

67
Q

What peptides are bound to MHC class 1

A

endogenous

68
Q

What peptides are bound to MHC class 2

A

exogenous

69
Q

What is the function of MHC class 1

A

elimination of viral cells by Tc cells

70
Q

What is the function of MHC class 2

A

elimination of extracellular organisms

71
Q

Does MHC class 1 use an invariant chain

A

No

72
Q

Does MHC class 2 use an invariant chain

A

yes

73
Q

Does MHC class 1 use Beta 2 microglobulin TAP

A

yes

74
Q

Does MHC class 2 use Beta 2 microglobulin TAP

A

no

LECOM Microbiology MS1 (22 decks)

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