Antigen Capture and Presentation to Lymphocytes

Question 1

TCR and MHC interaction

Answer 1

TCR/ T cells require MHC (MHC dependent)
peptide Ag at the MHC will interact with the variable region of the TCR
anchor residues of the peptide will anchor the Ag in the MHC pockets

Question 2

Recognition of antigens by antibodies

Answer 2

can be mem bound or soluble

broaber specifity than TCR: can recognize more than just peptides

Question 3

Migration of T lymphocytes

Answer 3

naive lymphocytes present in the LN, sample Ag

may encounter Ag and become active as an effector cell (Tc or Th), migrate to site

Question 4

APCs

Answer 4

macrophages
dendritic cells
b cells

Question 5

dendritic cell role

Answer 5

Question 6

macrophage APC role

Answer 6

Question 7

b cells APC role

Answer 7

Question 8

Function of cytotoxic T cells (CTLs)

Answer 8

Question 9

Role of Dendritic cells in antigen capture and presentation/ other important APCs?
what molecules does the DC use to recognize Ag?

Answer 9

found at skin, lungs, and GI: will capture Ag and migrate to peripheral LN or spleen
capable of recognizing the Ag via TLR or lecithin
once Ag is captured, cells lose adhesiveness for tissue and migrate and there is an increased expression of MHC and costimulators in the cell surface
will then interact with naive t cells to stimulate a t cell response

Macrophages and B lymphocytes are also important APCs

Question 10

Costimulators are important for?

Answer 10

antigen presentation by dendritic cells to activate naïve T cells.

Question 11

MHC

Answer 11

on APCs, will display Ag to TCR

Question 12

MHC genetics

Answer 12

complex genes, class I and II loci that are highly polymorphic

Question 13

class I MHC 
polymorphic regions 
peptide-binding cleft size
what binds TC coreceptor 
which t cells respond to these?

Answer 13

Polymorphic regions: a1 and a2
Peptide-binding cleft for peptides 8-9 aa long
a3 binds CD8 T-cell co-receptor
CD8+ T cells can only respond to antigen presented
by MHC class I molecules

Question 14

class II MHC 
polymorphic regions 
peptide-binding cleft size
what binds TC coreceptor 
which t cells respond to these?

Answer 14

Polymorphic regions: a1 and b1
a2 and b2 bind CD4 T-cell co-receptor
Peptide-binding cleft for peptides 10-30 aa long
CD4+ T cells can only respond to antigens presented by MHC class II molecules

Question 15

class II MHC on what cells

Answer 15

APCs

Question 16

class I MHC on what cells

Answer 16

all nucleated cells

Question 17

expression pattern of MHC alleles

Answer 17

codominant

Question 18

significance of polymorphic MHC genes

Answer 18

many alleles in population

different people can present and respond to different microbial antigens

Question 19

codominant expression of MHC significance

Answer 19

increases the number of possible MHC molecules

Question 20

broad specificity of MHC

Answer 20

many peptides can bind the same MHC

Question 21

how many peptides can each MHC molecule display at one time? why?

Answer 21

only one, each t cell responds to only one peptide at a time

Question 22

MHC molecules bind only?

Answer 22

peptides

Question 23

when are the peptides of MHC molecules acquired?

Answer 23

during intracellular assembly, I and II can display Ag/peptides from different intracellular compartments

Question 24

stable surface expression of MHC requires?

Answer 24

a peptide to be bound

Question 25

off rate of MHC

Answer 25

very slow, displays peptide long enough for T cell recognition

Question 26

CD8+ Cytotoxic T cells (CTLs) recognize?

Answer 26

endogenous (cytosolic) antigen presented by MHC class I molecules on an infected cell

Question 27

endogenous (cytosolic) antigen presentation mechanism?

Answer 27

Question 28

CD4+ Helper T cells recognize?

Answer 28

exogenous antigen presented by MHC class II molecules on a professional antigen presenting cell (APC)

Question 29

exogenous antigen presentation mechanism

Answer 29

Question 30

cross-presentation

Answer 30

Class I MHC-restricted cross-presentation of microbial antigens from infected cells by dendritic cells

Question 31

class II MHC pathway: Ag presentation to Th possible ways

Answer 31

two ways possible

microbe uptake by macrophage, present in endosome> use of class II to present Ag to CD4= cytokines to activate macrophage and kill microbe

Ag specific b cells bind extracellular Ag, present to Th via MHC II=cytokine production causing b cell to produce secreted Ab

Question 32

class I MHC pathway: presentation to Tc

Answer 32

cytosolic Ag> Ag peptide associated with MHC I and presented to CD8 which then activates killing function and kills infected cell