Cadet Exam 1

Question 1

Describe internalized (exogenous) antigens, MHC II

Answer 1

Uptake of extracell proteins into vesicular compartments of the antigen presenting cell
Processing of internalized proteins in endosomal and lysosomal vesicles
The expression of peptide MHC complexes on cell surface

Question 2

Describe the biosynth and transport of MHC II molecules to endosome

Answer 2

MHC II molecule is attached to the invariant chain to prevent any other peptide besides the antigen from binding
CLIP invariant chain is bound at the binding site
Once it enters the endosome the invariant chain is disassociated in acidic environment with endosome

Question 3

When does the processed peptides with an MHC II molecule associates?

Answer 3

This only happens after the invariant chain disassociated from MHC II molecule in the endosome and CLIP is released from peptide binding site

Question 4

Describe cytosolic (endogenous) antigens, MHC I

Answer 4

Proteins are produced in the cytosol

Ubiquitin binds the protein enters the proteasome and gets degraded to peptide fragments

Question 5

What are the fragment binder transported associated with antigen processing?

Answer 5

TAP (1 and 2)

Question 6

How does a peptide bind to an MHC I that are bridged to TAP via tapasin?

Answer 6

Peptide association stabilized the MHC and allows it to release from TAP so that it can be transported to the cell surface via exocytosis

Question 7

How does cross-presentation work?

Answer 7

Once a cell is infected to a virus it can be picked up by a host antigen presenting cell
APC will in turn cross-present the internalized infected cell to a virus-specific CD8+ cytotoxic T cell
Leads to a T cell response

Question 8

What does cross-presentation mean?

Answer 8

The infected cell does not directly present itself to the T cell but rather it’s antigen is displayed to the T cell via an APC

Question 9

What are MHC molecules?

Answer 9

Membrane proteins that contain a peptide-binding cleft at the amino-terminal end

Question 10

What are the human MHC cells?

Answer 10

Human Leukocyte Antigens

Question 11

How many peptides can bind to one MHC molecule?

Answer 11

Many

Question 12

How many T cells respond to a single peptide bound to an MHC?

Answer 12

One T cell for one peptide

Question 13

Describe the structure of the class I MHC.

Answer 13

Non-covalent assocated B-microglobulin
Peptide binding cleft made up of a1 and a2 (large enough for 8 to 11 amino acids)
Transient portion is a3 (invariant, binding sire for T-cell CD8)

Question 14

Describe the structure of the class II MHC.

Answer 14

Two chains - alpha and beta
Peptide binding cleft made up from a1 and b1 (10 to 30 amino acids)
Transmembrane portion is a2 and b2 (b domain = binding sire for T cell CD4)