Antigen Capture and Presentation to Lymphocytes

Question 1

B cell receptors recognize:

Answer 1

A variety of macromolecules in soluble or cell-surface form (i.e. proteins, polysaccharides, lipids, NAs).

Question 2

T cell receptors recognize:

Answer 2

Only small, linear peptides that have been generated intracellularly and displayed on an MHC.

Question 3

Anatomy of the T cell receptor (TCR)

Answer 3

2 polypeptide chains (a and b, with molecular weight of 50 kDa and 39 kDa).

Question 4

The variable regions constitute the:

Answer 4

Ag-binding site.

Question 5

The receptor contains 2 regions, known as the:

Answer 5

Constant and variable regions.

Question 6

T cells with y and d chains:

Answer 6

Poorly understood, but believed to have similar characteristics of ab T cells, but with a broader specificity for unconventional Ags, like HSPs and phospholipids.

Question 7

What makes up the TCR complex? (3)

Answer 7

TCR
aB or yd dimer
Association with CD3.

Question 8

Subunits in the TCR/CD3

Answer 8

1 y
1 d
2 E
2 z chains

Question 9

CD4+ binds:

CD8+ binds:

Answer 9

MHC II (Th)
MHC I (Tc)

Question 10

Expression of MHC II on DCs is:

Answer 10

Constitutive
Increases with maturation.
Increased by IFN-y.

Question 11

Expression of MHC II on macrophages is:

Answer 11

Low.

Inducible by IFN-y.

Question 12

Expression of MHC II on B cells is:

Answer 12

Constitutive.

Increased by IL-4.

Question 13

Ags captured by DCs are:

Answer 13

Taken to lymph nodes in the region.

NOT in the bloodstream (i.e. skin, GI tract, RT, etc.).

Question 14

Ags in the bloodstream are:

Answer 14

Captured by APCs in the spleen.

Question 15

Who produces IFN-y?

Answer 15

NK cells in innate immune reactions OR T cells during adaptive immune responses.

Question 16

IFN-y stimulates:

Answer 16

Expression of MHC II on APCs, which enhances activation of CD4+ cells.

Question 17

IFN-y and type I interferons stimulate:

Answer 17

Expression of MHC I molecules and the activatio of CD8+ cells.

Question 18

Class I genes (3):

Answer 18

HLA A, B, C.

Question 19

Class II gene (1) encodes, which produces (3):

Answer 19

HLA D.

HLA DP, DR, DQ molecules.

Question 20

MHC I bind peptides of how many AAs?

MHC II bind peptides of how many AAs?

Answer 20

8-10

10-20

Question 21

MHC I is made of:

Answer 21

A polymorphic a chain attached to a B2-microglobulin.

Question 22

What is glycosylated in the MHC I?

Answer 22

a chain.

Question 23

What is glycosylated in the MHC II?

Answer 23

a and b chains.

Question 24

MHC II is made of:

Answer 24

Polymorphic a and polymorphic b chains.

Question 25

MHC II is expressed only on:

Answer 25

Professional APCs: DCs, B cells, and Mo.

Question 26

MHC I is expressed on:

Answer 26

All nucleated cells.

Not RBCs.

Question 27

Peptides that bind MHC I are:

Answer 27

Generated from intracellular microbes (endogenous pathway).

Presented to CD8+ (Tc)

Question 28

Ags and pathogens that bind MHC II:

Answer 28

Are taken from the environment and extracellular.

Presented to CD4+ (Th).

Question 29

Anchor residues

Answer 29

Exist on peptides bound the MHC I/II grooves and vary for different MHC alleles.

Question 30

Ag recognition by TCR overview

Answer 30

TCR simultaneously recognizes AAs of the Ag and the MHC molecule displaying the peptide.

Question 31

A single MHC…

Answer 31

Can bind many different eptides with the same anchor residue.

Question 32

MHC II pathway in APCs overview (5):

Answer 32

1. Ag must be phagocytosed.
2. Must be processed by endosome/lysosome.
3. Must synthesize and transport MHC II to endosomes.
4. Peptides must associate with the MHC II.
5. MHC II expressed on cell surface.

Question 33

HLA-DM functions (3)

Answer 33

1. Causes dissociation of CLIP from peptide binding groove of MHC II.
2. Stabilizes and prevents degredation of binding groove of MHC II.
3. Facilitates the binding of Ag fragments onto the binding groove.

Question 34

CLIP function

Answer 34

Blocks binding groove of MHC II until an Ag binds.

Question 35

MHC I pathway overview:

Answer 35

1. Intracellular microbe degraded to peptides.
2. Peptides transported to the ER from the cytoplasm.
3. Assembly of MHC I complex in ER.
4. MHC I expressed on cell’s surface.

Question 36

Cross-presentation of Ags

Answer 36

Fragments of infected cells ingested by DCs.
Ags transported into the cytosol and processed to be presented on MHC I molecules.
Thus, DCs present extracellular Ags via MHC I pathway.

Question 37

Functions of:
ERAP
TAP

Answer 37

ERAP: involved in the final proteolytic processing of peptides to be presented on MHC I.
TAP: translocates peptides to the ER from cytosol.