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MIMM 214 > Linking Innate and Adaptive Immunity 5 > Flashcards

Linking Innate and Adaptive Immunity 5 Flashcards

1
Q

what is cross-presentation by DCs?

A

exogenous antigens are redirected to the endogenous presentation pathway and presented on MHC I

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2
Q

what are the only type of APCs that have been found to do cross-presentation?

A

dendritic cells

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3
Q

describe the redirection mechanism of cross-presentation by DCs

A

unclear!

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4
Q

what do we know about the redirection mechanism of cross-presentation by DCs?

A

DCs need a license/permission to redirect the exogenous antigen

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5
Q

how does the license for DCs work?

A

if DC presents an exogenous antigen to CD4+ helper T cell, it gets “licensed” to redirect the antigen into the endogenous pathway

i.e. antigen binds CD4+ T cell to activate it then activates DC

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6
Q

what is the license signal? what does this allow for?

A

cytokines sent btwn DC and CD4+ helper T cell

allows for antigen presentation on MHC I molecules to prime CD8+ T cell responses

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7
Q

what is required before the DCs receive a license?

A

must have activated CD4+ T cell!

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8
Q

what type of cells can present endogenous/cytosolic peptides by MHC II molecules?

A

any professional APC (DCs, macrophages, B cells)

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9
Q

by which process do MHC II molecules present cytosolic peptides? how does it work?

A

autophagy

digestion and breakdown by a cell of its own organelles and proteins in lysosomes

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10
Q

what is an autophagosome?

A

specialized vesicles that contain cytoplasmic content and fuse with lysosomes

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11
Q

describe the process of autophagy for antigen presentation

A
  1. parts of cytoplasm taken into autophagosomes
  2. proteins get degraded
  3. joins MHC II for exogenous pathway
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12
Q

describe an example of the presentation of cytosolic peptides by MHC II

A
  • virus infects macrophages and decreases expression of MHC I
  • macrophages redirect peptides to CD4+ cells to help clear infection
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13
Q

T cell responses are ____ restricted

A

T cell responses are MHC restricted

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14
Q

describe the experiment of incubating virus-infected target cells with cytotoxic T lymphocytes (CD8+) of same or different MHC haplotype

A

A. Both cell types have same haplotype –> lysis occurred because everything T recognizes the self-MHC molecule
B. Cell types have diff haplotype –> no lysis occurred because T cell can only recognize self-MHC molecule

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15
Q

what is MHC restriction?

A

a T cell can only recognize a peptide if it is presented by a self-MHC molecule

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16
Q

what is the exception to MHC restriction called?

A

allorecognition

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17
Q

what is allorecognition?

A

recognition of non-self MHC by some T cells in the body

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18
Q

what percent of all T cells can do allorecognition?

A

1-10% of all T cells in an organism

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19
Q

what does allogeneic mean?

A

non-self

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20
Q

what are non-self MHC molecules called?

A

allo-MHC

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21
Q

what is the consequence of allorecognition? why?

A

rejection of transplanted organs because people are genetically different so MHC is non-self and T cells attack

22
Q

what is an allele?

A

one specific form of a gene

23
Q

what is a locus?

A

the specific chromosomal location of a gene

24
Q

what type of gene is MHC coded by?

A

human leukocyte antigen (HLA)

25
Q

where and how is HLA found?

A

found in a cluster of genes on chromosome 6

26
Q

what are the 2 classes of MHC genes?

A
  1. MHC I genes
  2. MHC II genes
27
Q

what do MHC I genes code for? why?

A

only code alpha portion

B microglobulin is constant on another chromosome

28
Q

what are the 3 MHC I genes?

A
  1. HLA-A
  2. HLA-B
  3. HLA-C
29
Q

Describe the polymorphisms of MHC genes

A

multiple forms / alleles exist for each gene

30
Q

what is an allele in the context of polymorphisms?

A

2+ forms of a gene at a locus

31
Q

how many alleles do MHC genes have?

A

> 100

32
Q

what is the difference btwn HLA-A and HLA-A1?

A

HLA-A is a gene

HLA-A1 is an allele

33
Q

what is a haplotype?

A

combination of MHC alleles on 1 chromosome

34
Q

each individual inherits _____ haplotype from each parent

A

each individual inherits 1 haplotype from each parent

35
Q

MHC alleles are _________ expressed

A

MHC alleles CODOMINANTLY expressed

36
Q

what does it mean that MHC alleles are codominantly expressed?

A

both maternal and paternal MHC genes are expressed in offspring

37
Q

why is it good that MHC alleles are codominantly expressed?

A

best chance of presenting all possible antigen peptides it counters

38
Q

what is inherited from each parent for MHC I?

A

1 HLA-A, HLA-B, and HLA-C

39
Q

are humans homozygous or heterozygous? what consequence does this have?

A

heterozygous

hard to find transplant match

40
Q

describe the inheritance of many MHC I alleles and what this results in

A

inherit 3 different MHC I alleles from each parent (each have a similar function but different structure)

therefore 6 alleles can be expressed in 1 person

results in a high degree of variance in MHC expression

41
Q

what does a difference in alleles cause in the protein? what does this allow for?

A

causes a difference in amino acid locations within the groove sites

allows for presentation of a variety of peptides

42
Q

what would happen if the amino acids outside of the groove sites were to change?

A

could affect the structure conformation and folding of MHC molecule

43
Q

a given MHC molecule can bind 1 or many peptides?

A

a given MHC molecule can bind numerous peptides

44
Q

some peptides can bind 1 or many MHC molecules?

A

some peptides can bind many diff MHC molecules

45
Q

where does the variation of peptide binding groove usually occur on MHC II molecules?

A

on B1 chain

46
Q

what is polygeny?

A

many genes having same functions

47
Q

what are the 6 MHC II genes?

A
  1. HLA-DR
  2. HLA-DQ
  3. HLA-DP
  4. HLA-DM
  5. HLA-DOA
  6. HLA-DOB
48
Q

what is polymorphism?

A

multiple allelic variants of each gene in a population

49
Q

a b/b mouse mates with a k/k mouse, their progeny is b/k. can you transplant skin from b/k to b/b?

A

NO!!!! there will be peptides on b AND k MHC so 1-10% of b/b T cells will detect non-self (k) MHC and react

50
Q

can b/b donate to b/b or k/k parent or b/k progeny?

A

YES - b/b, b/k
NO - k/k

51
Q

can k/k donate to b/b or k/k parent or b/k progeny?

A

YES - k/k, b/k
NO - k/k

52
Q

can b/k donate to b/b or k/k parent or b/k?

A

YES - b/k
NO - b/b, k/k

MIMM 214 (33 decks)

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