Linking Innate and Adaptive Immunity 5

Question 1

what is cross-presentation by DCs?

Answer 1

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

Question 2

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

Answer 2

dendritic cells

Question 3

describe the redirection mechanism of cross-presentation by DCs

Answer 3

unclear!

Question 4

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

Answer 4

DCs need a license/permission to redirect the exogenous antigen

Question 5

how does the license for DCs work?

Answer 5

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

Question 6

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

Answer 6

cytokines sent btwn DC and CD4+ helper T cell

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

Question 7

what is required before the DCs receive a license?

Answer 7

must have activated CD4+ T cell!

Question 8

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

Answer 8

any professional APC (DCs, macrophages, B cells)

Question 9

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

Answer 9

autophagy

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

Question 10

what is an autophagosome?

Answer 10

specialized vesicles that contain cytoplasmic content and fuse with lysosomes

Question 11

describe the process of autophagy for antigen presentation

Answer 11

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

Question 12

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

Answer 12

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

Question 13

T cell responses are ____ restricted

Answer 13

T cell responses are MHC restricted

Question 14

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

Answer 14

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

Question 15

what is MHC restriction?

Answer 15

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

Question 16

what is the exception to MHC restriction called?

Answer 16

allorecognition

Question 17

what is allorecognition?

Answer 17

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

Question 18

what percent of all T cells can do allorecognition?

Answer 18

1-10% of all T cells in an organism

Question 19

what does allogeneic mean?

Answer 19

non-self

Question 20

what are non-self MHC molecules called?

Answer 20

allo-MHC

Question 21

what is the consequence of allorecognition? why?

Answer 21

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

Question 22

what is an allele?

Answer 22

one specific form of a gene

Question 23

what is a locus?

Answer 23

the specific chromosomal location of a gene

Question 24

what type of gene is MHC coded by?

Answer 24

human leukocyte antigen (HLA)

Question 25

where and how is HLA found?

Answer 25

found in a cluster of genes on chromosome 6

Question 26

what are the 2 classes of MHC genes?

Answer 26

1. MHC I genes 2. MHC II genes

Question 27

what do MHC I genes code for? why?

Answer 27

only code alpha portion B microglobulin is constant on another chromosome

Question 28

what are the 3 MHC I genes?

Answer 28

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

Question 29

Describe the polymorphisms of MHC genes

Answer 29

multiple forms / alleles exist for each gene

Question 30

what is an allele in the context of polymorphisms?

Answer 30

2+ forms of a gene at a locus

Question 31

how many alleles do MHC genes have?

Answer 31

>100

Question 32

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

Answer 32

HLA-A is a gene HLA-A1 is an allele

Question 33

what is a haplotype?

Answer 33

combination of MHC alleles on 1 chromosome

Question 34

each individual inherits _____ haplotype from each parent

Answer 34

each individual inherits 1 haplotype from each parent

Question 35

MHC alleles are _________ expressed

Answer 35

MHC alleles CODOMINANTLY expressed

Question 36

what does it mean that MHC alleles are codominantly expressed?

Answer 36

both maternal and paternal MHC genes are expressed in offspring

Question 37

why is it good that MHC alleles are codominantly expressed?

Answer 37

best chance of presenting all possible antigen peptides it counters

Question 38

what is inherited from each parent for MHC I?

Answer 38

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

Question 39

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

Answer 39

heterozygous hard to find transplant match

Question 40

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

Answer 40

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

Question 41

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

Answer 41

causes a difference in amino acid locations within the groove sites allows for presentation of a variety of peptides

Question 42

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

Answer 42

could affect the structure conformation and folding of MHC molecule

Question 43

a given MHC molecule can bind 1 or many peptides?

Answer 43

a given MHC molecule can bind numerous peptides

Question 44

some peptides can bind 1 or many MHC molecules?

Answer 44

some peptides can bind many diff MHC molecules

Question 45

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

Answer 45

on B1 chain

Question 46

what is polygeny?

Answer 46

many genes having same functions

Question 47

what are the 6 MHC II genes?

Answer 47

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

Question 48

what is polymorphism?

Answer 48

multiple allelic variants of each gene in a population

Question 49

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?

Answer 49

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

Question 50

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

Answer 50

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

Question 51

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

Answer 51

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

Question 52

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

Answer 52

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