MHC and Antigen Presentation to T cells

Question 1

T cell receptor (TCR) is composed of 2 polypeptide chains ____ and ____

which are made up of ____ and ____ regions

Answer 1

alpha and beta

constant and variable

Question 2

the genes coding for TCR, CD3, CD4, CD8, and MHC are members of the ____ super family

Answer 2

Ig

Question 3

unlike Abs, TCRs do not recognize native antigen, but can only bind processed Ag presented in associated with ____ molecules

Answer 3

MHC

Question 4

unlike BCR (Abs), TCR are never produced in a ______ form

Answer 4

secreted

Question 5

the ____ region of alpha and beta chains of TCR constitute the Ag-binding site

Answer 5

variable

Question 6

some unconventional T cells express a TCR consisting of ____ and ____ chains

Answer 6

gamma and delta

Question 7

gamma/delta T cells have a broader specificity for unconventional Ag such as ____ and ____

(don’t need APCs for activation)

Answer 7

HSPs and phospholipids

Question 8

TCR is associated with nearby ___ signaling complexes

Answer 8

CD3

composed of gamma, delta, and epsilon chains

Question 9

____ Ags are presented to T cells in association with MHC molecules

Answer 9

peptide

Question 10

class I MHC is expressed on all

Answer 10

nucleated cells

Question 11

class II is expressed on

Answer 11

professional Ag-presenting cells (DCs, mast cells, B cells)

Question 12

in class I MHC, what chain(s) contributes to peptide binding groove

Answer 12

only alpha chain

Question 13

in class II MHC, what chain(s) contributes to peptide binding groove

Answer 13

both alpha and beta

Question 14

what MHC binds smaller peptides

Answer 14

MHC class I

Question 15

CD4 (Th cells) recognize Ags presented by class ___ MHC

Answer 15

class II

Question 16

CD8 (cytotoxic T cell) recognize Ags presented by class ____ MHC

Answer 16

class I

Question 17

MHC/HLA loci is located on Chromosome

Answer 17

6

Question 18

______ ______ refers to a discotinuous genetic variation resulting in the occurrence of several different types of individual molecules

Answer 18

molecular polymorphism

Question 19

class I genes (HLA-A, -B, -C) encode a polymorphic heavy chain which is expressed together with beta2-microglobulin and on the surface of all nucleated cells for Ag recognition by _____ T cells

Answer 19

CD8+

Question 20

class II genes (HLA-DP, -DR, -DQ) which are expressed on the surface as alpha and beta polymorphic polypeptide chains on APCs for Ag recognition by _____ T cells

Answer 20

CD4+

Question 21

in class I molecules, the ____ chain is glycosylated

Answer 21

alpha

Question 22

in class II molecules, the ____ chain is glycosylated

Answer 22

both alpha and beta

Question 23

_____ ______ on the peptides bind to residues in the class I and class II grooves and vary for different MHC alleles

Answer 23

anchor residues

Question 24

the cleft of class I molecules are _____ whereas the cleft of class II molecules are _____

Answer 24

closed

open

Question 25

HLA class II molecules are expressed on

Answer 25

professional APCs (e.g. B cells, dendritic cells, and macrophages)

Question 26

HLA class I molecules are expressed on

Answer 26

all nucleated cells

Question 27

expression of MHC class I and/or II molecules is modulated by

Answer 27

cytokines

Question 28

peptides that bind to class I MHC molecules are derived from ______ microbes that have infected host cells

Answer 28

intracellular | endogenous pathway

Question 29

peptides that bind to class I MHC are recognized by what cells

Answer 29

CD*+ cytotoxic T cells

Question 30

Ags and extracellular pathogens taken from the environment are primarily presented on class ____ MHC molecules and presented to what cells?

Answer 30

II CD4+ helper T cells

Question 31

function of dendritic cells as APC

Answer 31

naive T cell activation: clonal expansion and differentiation into effector T cells

Question 32

function of macrophages as APC

Answer 32

effector T cell response: macrophage activation (cell-mediated immunity)

Question 33

function of B cell as APC

Answer 33

effector T cell response: B cell activation and antibody production (humoral immunity)

Question 34

_____ is a costimulatory protein found on professional APCs and binds to its ligand ______ which is found on T-cells and is required for coactivation

Answer 34

CD40 CD40L

Question 35

DCs expression of Class II MHC

Answer 35

constitutive

Question 36

Macrophage expression of class II MHC

Answer 36

low; induced by IFN-gamma

Question 37

B lymphocyte expression of class II MHC

Answer 37

constitutive; induced by IL-4

Question 38

Ags that enter the blood stream are captured by APCs in

Answer 38

the spleen

Question 39

APCs don't live in ______ but do live in ______

Answer 39

lymph nodes spleen

Question 40

activated NK cells produce ____ during innate immune reactions; this stimulates _____ expression on APCs and thus enhances Ag presentation and activation of CD4+ and CD8+ T cells

Answer 40

IFN-gamma MHC

Question 41

B cells require _____ for isotype switching from IgM

Answer 41

CD40/CD40L interaction

Question 42

how do T cells recognize antigens

Answer 42

recognize only linear peptides | conformation is lost during enzymatic processing of protein Ags into peptides

Question 43

T cells recognize cell-associated antigens, not _____ antigens

Answer 43

soluble

Question 44

MHC class II molecules display peptides that are taken up from ______ environment of APCs by mechanisms of either pinocytosis (DCs and B cells) or phagocytosis (macrophages)

Answer 44

extracellular

Question 45

MHC class I molecules present peptides generated in the proteasome from ______ proteins including proteins from ______ pathogens

Answer 45

cytosolic intracellular

Question 46

CD4+ T cells recognize what type of Ags acquired by professional APCs?

Answer 46

extracellular

Question 47

CD8+ T cells recognize what type of Ags?

Answer 47

Ags derived from intracellular proteins

Question 48

class I MHC pathway

Answer 48

1. production of proteins in the cytosol (virus) 2. virus peptides are tagged by ubiquinase and sent to proteosome for proteolytic degradation of proteins 3. transport of peptides from cytosol to ER 4. assembly of peptide-MHC class I complexes in ER 5. peptide-MHC class I complex is sent to Golgi Apparatus to be vesicular 5. surface expression of peptide-MHC class I complexes

Question 49

TAP

Answer 49

transporter to get peptides into ER

Question 50

class II MHC pathway

Answer 50

1. uptake of extracellular proteins into vesicular compartments of APC 2. processing of internalized proteins in endosomal/lysosomal vesicles (forms phagolysosome) 3. synthesis and transport of class II MHC molecules from ER to endosome 4. association of processed peptides with class II MHC molecules in vesicles 5. expression of peptide-MHC complexes on cell surface

Question 51

there are a lot of self peptides synthesized in the ER which are prevented from binding to class II MHC by the ______ chain

Answer 51

invarient

Question 52

protein HLA-DM removes the invariant chain and allows the ______ of extracellular Ags into class II MHC

Answer 52

loading

Question 53

the HLA-DM editing mechanism works to ensure the presentation of only the protein fragments most relevant for eliciting an immune response. HLA-DM has 3 major functions: HLA-DM causes the dissociation of ______ from the peptide binding groove of MHC II HLA-DM stabilizes and prevents ______ of the empty MHC II HLA-DM facilitates the binding of Ag fragments to the ______ stabilized binding groove

Answer 53

CLIP degradation open

Question 54

CLIP is a protein that binds MHC class II and acts as a ______ so nothing else binds to it

Answer 54

placeholder

Question 55

cross presentation

Answer 55

excellular pathogens get presented to CD8+ T cells via MHC-II

Question 56

cross-presentation pathway

Answer 56

1. some extracellular pathogens brought in b phagocytosis leak into the cytoplasm and are treated as intracellular pathogen 2. gets tagged by ubiquitin 3. digested by proteosome 4. transport of peptides through TAP into ER 5. assembly of peptide-MCH I complex in ER 6. exocytic vesicle allows for surface expression of peptide-MHC I complex

Question 57

immunodominant peptides: immunodominant peptides are obtained by ______ available in the cell the peptides bind best to the available class I and II MHC molecules thus, immune responses will be generated against ______ Ags based on the available proteases and MHC molecules

Answer 57

proteases dominant Ags

Question 58

why aren't erythrocytes which don't express class I MHC not destroyed by NK cells

Answer 58

NK cells spare cells that express "markers of normal self" in the form of MHC class I molecules, and eliminate them when these markers are absent or insufficiently expressed

Question 59

CD47

Answer 59

glycoprotein consistently expressed on RBCs that serves as a marker of self

Question 60

CD47 binds to

Answer 60

inhibitory receptor on NK cells

Question 61

activated Th1 cells help ______ to get rid of ______ microbes and help development of cytotoxic T cells

Answer 61

macrophages intracellular

Question 62

cytokine IFN-gamma produced by ______ activated macrophages

Answer 62

Th1 cells | also NK cells

Question 63

activated Th2 cells are mainly involved in responses against _______ microbes helping _______ cells to develop into memory cells and plasma cells that produce antibodies

Answer 63

extracellular B

Question 64

cytokine IL-4 is produced by _______ cells and is important for ______ cell proliferation

Answer 64

Th2 B