Antigen Processing

Question 1

Describe the process of Intracellular pathogen presentation.

Answer 1

1. Proteins are in the cytosol and tagged with ubiquitin via ubiquitin ligase and degraded by proteasome to produce peptides in cytoplasm.
2. Peptides are transported into ER lumen by TAP.
3. Peptides loaded onto MHC class 1 in ER lumen.
4. MHC 1-peptide complex transported to CM for presentation.

Question 2

Explain Cross-Presentation.

Answer 2

1. Dendritic cells (only) phagocytoses infected cell or tumor cell.
2. Phagocytosed cell is digested in phagolysosome.
3. Some of the peptides are loaded into MHC 2.
4. The rest is taken out of phagolysosome and into cytoplasm.
5. The protein is degraded by a proteosome
6. Peptides are transported into ER lumen and loaded into MHC 1.

Question 3

What do MHC molecules bind to?

Answer 3

They bind to the CD4 or CD8. NOT to the antigen or the TCR.

Question 4

When a tumor cell is attacked by a CD8, how does that cell die?

Answer 4

It dies by apoptosis, NOT osmotic lysis.

Question 5

What is the advantage of cross-presentation?

Answer 5

It can activate both CD4 and CD8.

Question 6

What building block does MHC 1 and 2 bind?

Answer 6

ONLY PEPTIDES

Question 7

How doe herpes simplex avoid the immune system?

Answer 7

Inhibits antigen presentation; An HSV protein interferes with the TAP transporter.

Question 8

How does Cytomegalovirus avoid the immune system?

Answer 8

Inhibits proteasomal acitivity; Removal of MHC 1 molecules from ER.

Question 9

How does the Epstein-Barr virus avoid the immune system?

Answer 9

Inhibition of proteasomal activity.