Antigen Processing and Presentation

Question 1

What is antigen presentation and processing

Answer 1

Protein broken down into peptide that can be presented to T cells by MHC

Question 2

Why is antigen presenattion and processing necesary

Answer 2

Ensures that the immune system can recognize and respond to a wide variety of pathogens

Question 3

3 molecules involed in antigen presentation

Answer 3

1. APC
2. MHC
3. TCR

Question 4

which MHC has a wider peptide binding cleft

Answer 4

MHC II which allows it to bind more varied peptides

Question 6

What kind of epitopes can be recognized by T cells

Answer 6

Peptides (short chain amino acids)

Question 7

Examples of intracellular pathogens -3

Answer 7

1. Virus - HIV, HMPV, COVID, Influenza
2. Bacteria- Listeria monocytogens, Salmonella, TB
3. Protozoa - Plasmodium spp, Toxoplasma gondii

Question 8

Extracellular pathogens

Answer 8

1. Bacteria - Strepto pneu, Staphylococcus aur, E.coli
2. Fungi - Candida albicans, aspergillus
3. Parasite - Giardia Lamblia, trypanosoma brucei

Question 9

Processing endo antigens

Answer 9

• Marked by ubiquitin
• Recognized by proteasome and broken down to peptides
• Transported by TAP to ER then binds MHC I
• rec by CD8+ T cells

Question 10

Processing exo antigens

Answer 10

• Phagocytosed by the APC
• Engulfed into Proteasome
• Broken down into peptides by Lysosomes
• MHC II
• CD4 cells, which recruit other immune cells for an effective immune response

Question 11

TCR - 4

Answer 11

1. molecules on the surface of a T cell
2. two polypeptide chains joined by a disulphide bond
3. alpha and beta chain
4. delta and gamma chain

Question 12

How is the TCR formed

Answer 12

through a process of VDJ

Question 13

the beta subunits mainly funtion in

Answer 13

recognizition.

Question 13

MHC I structure

Answer 13

alpha chain produced by MHC gene and B chain produced by beta 2 microglobulin

Question 14

MHCII structure

Answer 14

alpha and beta chain produced by MHC genes

Question 15

6 key steps in antigen presentation

Answer 15

1. Acquisition of antigens = by phagocytosis/endocytosis through the endocytic pathway
2. Tagging of antigens for proteolysis into peptides = lysosomal protease or proteasome
3. Proteolyss = same enzymes
4. Delivery of antigens to MHC = TAP complex and ERAAP(trimming of peptide size so they are able to bind the MHC molecules)
5. Loading of peptides to MHC = TAP and Tapasin
6. Display of MHC on the cell surface

Question 16

Evasion strategies by pathogens - 3

Answer 16

1. Hepesvirus, Adenovirus, Poxvirus
2. Detain the MHC molecules intracellularly
3. Encode proteins that interefer with the activity of the MHC encoded TAP molecules

Question 17

Hepes virus evasion strategy

Answer 17

encodes for proteins that structurally resemble MHC molecules

Question 18

Class 1 co stimulation

Answer 18

Fas and Fas- ligand

Question 19

Class 2 co stimulation

Answer 19

B7 and CD28

Question 20

B cell co stimulation

Answer 20

CD40 and CD40L

Question 21

Benefits of antigen presentation -2

Answer 21

1. Stimulate antigen presentation
2. Initiate

Question 22

How autoimmune diseases develop

Answer 22

• MHC molecules present antigens (self and non) to T cells
• T cells need to recognize if the T cells is self/ non self and act accordingly
• If T cell fails to do this, an autoimmune disease can arise

Question 23

Antigen presentation in transplants

Answer 23

The MHC molecules of the donor and recipient must match for a transplant to be successful