Adaptive Immunity activation

Question 1

Class I MHC

who expresses, what do they present

Answer 1

all nucleated cells (obviously not RBCs)
they present peptides 8-11 amino acids in length
“present endogenously processed peptides”

Question 2

How many genes do humans have for the MHC 1 complex?

Answer 2

3, coding for 6 alleles (one from each parents)

HLA-A
HLA-B
HLA-C

highly polymorphic and co-dominantly expressed

Question 3

What is significant about polymorphic proteins?

Answer 3

they have the same shape but they differ by one or a few amino acids

Question 4

how many allotypes of HLA-A and HLA-B are there?

Answer 4

200- A

400- B

Question 5

what about the beta-2 protein?

Answer 5

it is not polymorphic.

Question 6

what recognizes MHC class I?

Answer 6

CD8 cytotoxic lymphocytes

Question 7

what does it mean to say CD*+ T cells express endogenous peptides?

Answer 7

these are intracellular pathogens like viruses that infect the host cell

“surface protein fragments manufactured by the cells”

Question 8

MHC I hold peptides of what length?

Answer 8

8-9 a.a. long

Question 9

what kind of bonds are at work between the peptide and the MHC and TCR?

Answer 9

non-covalent interactions

Question 10

what components of the MHC holds to the peptide?

Answer 10

alpha1 and alpha2

Question 11

CD8 does what

Answer 11

stabilizes interaction between TCR and MHC

Question 12

the CDR is on the _______

Answer 12

TCR

Question 13

is the CDR on the MHC or the TCR

Answer 13

TCR

Question 14

where are HLA-gene coded regions on the MHC?

Answer 14

the alpha1 and alpha2 peptide binding region

Question 15

where does CD8 bind on the MHC 1 molecule?

Answer 15

on the alpha3 region

Question 16

what’s the order of the CDR regions from the lateral edges of the CDR regions to the most medial

Answer 16

CDR2-CDR1-CDR3

Question 17

in the interior of the cell, what are MHC I’s doing?

Answer 17

sampling all the proteins

Question 18

what are CTLs doing?

Answer 18

always sampling the MHC I of all the cells it contacts

Question 19

Ag processing for class I MHC

how does it happen, what significant proteins are involved

Answer 19

old proteins are destroyed by the proteosome and chopped into pieces IN THE CYTOPLASM

transport proteins tap 1 and 2 carry all the garbage peptides out into the endoplasmic reticulum

these peptides become loaded into the grooves of class I MHC

Question 20

Class II MHC: polymorphic or not

Answer 20

HIGHLY polymorphic

Question 21

What size peptides do MHC II hold?

Answer 21

13-25 a.a.

Question 22

Structure of MHC II

Answer 22

two non-covalently bonded peptide chains (alpha 1 and beta 1) both are highly polymorphic.

Question 23

what parts of the MHC do the peptides interact with?

Answer 23

both the alpha 1 and beta 1 chains which have CDR

Question 24

the regions where the CD4 interacts with the MHC II is called

Answer 24

conservative

Question 25

MHC I was loaded in the endoplasmic reticulum, where are MHC II's loaded?

Answer 25

in endosomes

Question 26

the invariant chain: GO!

Answer 26

MHC II is synthesized in the endoplasmic reticulum; before it leaves, it's loaded with an "invariant" chain to prevent it from grabbing any self-peptides as it travels around the cell. inside the transport vesicle the invariant chain is cleaved to the "clip fragment"

Question 27

clip

Answer 27

what remains of the invariant chain after it's been degraded in the endosome, it's the surrogate peptide in the MHC II until HLA-DM facilitates the release

Question 28

HLA-DM

Answer 28

facilitates clips release from MHC II so peptides can be loaded

Question 29

From where do the peptides that MHC II loads come from?

Answer 29

from phagocytized/endocytized/pinocytized

Question 30

CD8 binds to the ____ domain of the MHC I molecule

Answer 30

alpha3

Question 31

CD4 binds to the ___ domain of the MHC II molecule

Answer 31

beta2

Question 32

broadly speaking, what distinguishes MHC I and II from one another apart from the big things?

Answer 32

MHC I seems to display intracellular pathogens and MHC II displays danger signals from outside the cell there is the exception of cross presentation

Question 33

the exogenous presentation of peptides via the MHC class 1 pathway is achieved how?

Answer 33

cross presentation

Question 34

explain cross presentation

Answer 34

this is when peptides usually presented by MHC I are picked up exogenously: say a virus infected cell dies, and the cellular detritus is picked up by a professional APC.... because it's exogenous, we expect MHC II because these are viral materials, we also expect MHC I the cell solves this by leaking the peptides into the cytoplasm, thus they will be treated by MHC I in an MHC II carrying cell

Question 35

the "short version" of cross presentation

Answer 35

when professional APCs present exogenous material via the MHC I pathway. the debris was "leaked" into the cytoplasm and thus processed via the proteosome.

Question 36

Ags recognized by B cells can be in what forms

Answer 36

soluble are cell surface associated form

Question 37

effector B cells are found where

Answer 37

lymphoid organs

Question 38

What are the two B cell surface BCRs?

Answer 38

IgM and IgD

Question 39

What are the components of the BCR complex?

Answer 39

the BCR and two other peptides: Igbeta/Igalpha

Question 40

What are Igalpha/Igbeta?

Answer 40

they are associated disulfide linked heterodimers which, when BCRs bind an epitope, initiated an intracellular signaling cascade that leads to B cell activation

Question 41

TCR's are composed of

Answer 41

alpha and beta chains

Question 42

what makes the TCR chains what they are

Answer 42

they both have constant and variable regions

Question 43

TCRs are associated with what molecules?

Answer 43

3 invatiant domains epsilon-delta ----- gamma-epsilon and two zeta chains underneath the TCR complex

Question 44

CD3

Answer 44

identification marker for TCR epsilon delta and gamma epsilon

Question 45

What do APCs need besides the MHC to stimulate T cells?

Answer 45

co-stimulators

Question 46

resting-APC

Answer 46

MHC expression w/out co-receptor expression

Question 47

activated-APC

Answer 47

MHC expression + co-receptor

Question 48

Non-traditional gamma-delta T cells where are they a major population, what's interesting about their CD expressions, their significance

Answer 48

``` They don't express CD4/CD8 reside largely in epithelia tissues recognition of lipid antigens have no memory cells TCR repertoire is limited ```