Lecture 6: Adaptive Immunity 3- Part 2

Question 1

what are two antigen presenting pathways?

Answer 1

• Endogenous antigens in cytosol- presented on class I MHC to CD8* cytotoxic T Cells
• Exogenous antigens in endosomes presented to class II MHC molecules to CD4* T helper cells

Question 2

Endogenous antigens- generations of class I MHC peptides

Answer 2

• Produced from proteins produced inside the cell
• include self proteins and foreign (virus)
• Class I MHC antigens activate Cytotoxic CD8-T cells for the killing the infected cells and tumour cells

Question 3

What is a TAP protein?

Answer 3

Transporters associated with Antigen Processing

Question 4

Describe the structure of TAP proteins and how many are there?

Answer 4

form a heterodimer

with TAP 1 and TAP 2

Question 5

What is the function of the TAP proteins?

Answer 5

-Selective transport peptides from the cytoplasm into the lumen of the ER

Question 6

What size amino acids can the TAP pump proteins transport?

Answer 6

8-16 amino acids long

Question 7

MHC class I molecules consists of two types of chains

Answer 7

• Polymorphic heavy chain

- β2-microglobulin.

Question 8

What is class I heavy chain is stabilised by?

Answer 8

Calnexin- until -β2-microglobulin binds

Question 9

How is the heterodimer class I heavy chains and β2 stablised by once the Calnexin is released?

Answer 9

The heterodimer forms the peptide loading complex with calreticulin, Erp57, tapasin and TAP.

Question 10

what happens to the peptide delivered by TAP?

Answer 10

-Peptide delivered by TAP binds to the class I heavy chain forming the mature MHC class 1 molecule

Question 11

what happens to Class I molecule?

Answer 11

-Disassociates from the peptide-loading complex and exported from the ER

Question 12

what activates the CD8* +Tc ?

Answer 12

-Endogenous or intracellular antigen

Question 13

What is the purpose of CD8+Tc?

Answer 13

• Needed for eradication of infected cells

- Can be activated against the tumour target

Question 14

Why must the antigens stimulating CD8* produced inside the cell?

Answer 14

• Virus, some bacteria and parasite live inside the host cells
• therefore antigens stimulating CD8+ must be produced inside the cell- to alert the immune system

Question 15

How do the virus evade immune system?

Answer 15

-can interfere with class I MHC expression to escape killing by CD8+

Question 16

How does the HSV evade the immune system?

Answer 16

• HSV protein ICP47 can selectively bind to TAP and inhibit the transfer of peptides into ER

Question 17

How do some parasites evade immune system?

Answer 17

-invade de-nucleated red blood cells that do not express MHC I