MHC I/II + Ag Processing

Question 1

List the professional APC

Answer 1

DC - most important
M0
B cells

Question 2

What are DCs essential for?

Answer 2

Essential for initiating new T cell/immune response

Primes initial immune response - M0 + B cells can help w/recall memory + aid in effector function

Question 3

Describe what DC looks like

Answer 3

‘Hairy looking cells’ - on electro-micrograph

Identified by Ralph Steinman

Question 4

What is the main role of DCs?

Answer 4

To patrol areas where pathogens exist

Process Ag from wide variety pathogens

Question 5

What happens once the DC takes up the Ag?

Answer 5

Once take up + process Ag, immediately leave initial site of infection
Migrate to lymph nodes via afferent lymph vessels where educate T cells to respond
ie. trigger Ag presentation pathway

Question 6

Where are DCs found?

Answer 6

Under most surfaces epithelia + in solid organs

Question 7

Are there subtypes of DCs?

Answer 7

Lots specialised DC eg. tissue resident/specific

Many sub-types - all work to generate Ag in different types of infection

Question 8

Describe receptor mediated phagocytosis

Answer 8

Bact/viruses specifically recognise receptors on surface DCs + get taken up

Question 9

Describe macropinocytosis

Answer 9

Works to do general surveillance of environment

Drinks up whatever is in the env - so material is internalised incl. viruses, bacteria, soluble Ag

Question 10

What happens after pino/phagocytosis?

Answer 10

Peptides are processed + presented via MHC II

Triggers responses from CD4 cells

Question 11

Describe direct viral infection as a route for Ag processing + presentation by DC

Answer 11

Virus is in cytosol + replicates there
peptides are broken down + presented by MHC I
Educate CD8 cells

Question 12

Describe cross-presentation after phagocytic/macropinocytic uptake or transfer from incoming DC to resident DC

Answer 12

Take up materials/debris from other cells/ take up other DC

Material broken down in cytoplasm + presented through MHC I - CD8 cells educated

Question 13

Describe the 2 routes entry: exogenous + endogenous pathway

Answer 13

Exogenous - breakdown material taken up by phagocytosis
presented through MHC II - response CD4 cells

Endogenous - cytosolic pathway, material broken down + presented through MHC-1
Educates CD8 cells

Link between MHC class + T cell education is how process Ag

Question 14

How do DC enter the lymph nodes?

Answer 14

Chemokine concentration gradient followed by DC to enter into lymph nodes

Specialised BV (high endothelial venules - HEV) secrete CCL21 - attracts DC

DC have receptor for it which attracts down gradient + home in on lymph nodes

Should have T cells + DC arriving with processed Ag to initiate response

CCL21 contributes to DC maturation