Antigen Presentation

Question 1

What is antigen presentation?

Answer 1

displaying of peptides derived from pathogens derived from pathogens or other proteins on the dendritic cell surface in a way that T-cells can see

Question 2

What is the structure of MHC class 1?

Answer 2

• expressed on nucleated cells

- transmembrane alpha chain + beta2 micro globulin, the peptide binding groove is in the alpha chain

Question 3

What is the structure of the MHC class 2?

Answer 3

• expressed only on antigen presenting cells such as dendritic cells, B cells, macrophages, thymic epithelial
• 2 non-identical transmembrane polypeptide chains (alpha and beta), peptide groove is in-between

Question 4

What are the steps of the endogenous pathway?

Answer 4

1. intracellular proteins are degraded into peptides by proteasome
2. TAP proteins transport peptides from cytoplasm to the lumen of the ER
3. peptide binds to MHC 1 protein

Question 5

What are the steps of the exogenous pathway?

Answer 5

1. endocytosis/phagocytosis of the pathogen/ MHC class II is associated with invariant chain leaves the ER
2. endo/phagosome fuses to lysosome that contains lysozyme, degrades the proteins into peptides
3. vesicle with MHC II fuses with the vesicle that contains peptide fragments
4. invariant chain degrades into CLIP, CLIP gets replaced with peptide

Question 6

What is the cross-pathway?

Answer 6

pathogen gets presented by both MHC-1 and MHC-2

Question 7

What is the purpose of positive T-cell selection?

Answer 7

to generate diversity, and impose MHC restriction

Question 8

What is the purpose of negative T-cell selection?

Answer 8

The AIRE protein exposes T-cells to cells from different parts of the body, and T-cells that bind with high affinity to MHC are killed