Immunology Chapters 5 & 6 Examination 2026 – UCF
1. Which molecule is responsible for transporting peptides from the cytosol into
the lumen of the endoplasmic reticulum for MHC Class I loading?
A. HLA-DM
B. Calnexin
C. TAP (Transporter associated with antigen processing)
D. Invariant chain
Answer: C
Rationale: TAP is a heterodimer in the ER membrane that pumps peptides produced by
the proteasome into the ER lumen.
2. Which of the following describes the structure of the T-cell receptor (TCR)
heterodimer?
A. An alpha chain and a beta chain
B. Two heavy chains and two light chains
C. An alpha chain and a beta-2 microglobulin
D. Four polypeptide chains linked by disulfide bonds
Answer: A
Rationale: The majority of T cells express a TCR consisting of one alpha chain and one beta
chain.
,3. MHC Class II molecules primarily present antigens derived from which
location?
A. Extracellular environment (via endosomes)
B. Nucleus
C. Cytosol
D. Mitochondria
Answer: A
Rationale: MHC Class II molecules present exogenous antigens that have been internalized
into endocytic vesicles.
4. The proteasome is primarily involved in the degradation of proteins for
presentation on which molecule?
A. MHC Class I
B. MHC Class II
C. CD3
D. TCR alpha chain
Answer: A
Rationale: The proteasome degrades intracellular proteins into peptides for the MHC Class
I pathway.
5. What is the role of the invariant chain (Ii) in the MHC Class II pathway?
A. To transport peptides into the ER
B. To stabilize the MHC Class I molecule
C. To trim long peptides into shorter fragments
D. To block the peptide-binding groove in the ER and guide the molecule to endosomes
Answer: D
Rationale: The invariant chain prevents premature peptide binding in the ER and targets
the MHC II complex to the MIIC compartment.
, 6. Which enzyme is responsible for adding N-nucleotides during junctional
diversity of TCR gene rearrangement?
A. RAG-1
B. DNA-PK
C. Terminal deoxynucleotidyl transferase (TdT)
D. Artemis
Answer: C
Rationale: TdT adds non-templated nucleotides (N-nucleotides) to the junctions between
gene segments, increasing diversity.
7. Which molecule functions as a molecular chaperone to stabilize the MHC
Class I heavy chain before beta-2 microglobulin binds?
A. Tapasin
B. Calnexin
C. Calreticulin
D. ERp57
Answer: B
Rationale: Calnexin is the initial chaperone that binds the MHC Class I heavy chain in the
ER.
8. What is the typical length of peptides that bind to MHC Class I molecules?
A. Over 30 amino acids
B. 13-25 amino acids
C. 8-10 amino acids
D. 5-7 amino acids
Answer: C
Rationale: MHC Class I molecules have a closed binding groove that accommodates short
peptides, usually 8 to 10 amino acids long.
1. Which molecule is responsible for transporting peptides from the cytosol into
the lumen of the endoplasmic reticulum for MHC Class I loading?
A. HLA-DM
B. Calnexin
C. TAP (Transporter associated with antigen processing)
D. Invariant chain
Answer: C
Rationale: TAP is a heterodimer in the ER membrane that pumps peptides produced by
the proteasome into the ER lumen.
2. Which of the following describes the structure of the T-cell receptor (TCR)
heterodimer?
A. An alpha chain and a beta chain
B. Two heavy chains and two light chains
C. An alpha chain and a beta-2 microglobulin
D. Four polypeptide chains linked by disulfide bonds
Answer: A
Rationale: The majority of T cells express a TCR consisting of one alpha chain and one beta
chain.
,3. MHC Class II molecules primarily present antigens derived from which
location?
A. Extracellular environment (via endosomes)
B. Nucleus
C. Cytosol
D. Mitochondria
Answer: A
Rationale: MHC Class II molecules present exogenous antigens that have been internalized
into endocytic vesicles.
4. The proteasome is primarily involved in the degradation of proteins for
presentation on which molecule?
A. MHC Class I
B. MHC Class II
C. CD3
D. TCR alpha chain
Answer: A
Rationale: The proteasome degrades intracellular proteins into peptides for the MHC Class
I pathway.
5. What is the role of the invariant chain (Ii) in the MHC Class II pathway?
A. To transport peptides into the ER
B. To stabilize the MHC Class I molecule
C. To trim long peptides into shorter fragments
D. To block the peptide-binding groove in the ER and guide the molecule to endosomes
Answer: D
Rationale: The invariant chain prevents premature peptide binding in the ER and targets
the MHC II complex to the MIIC compartment.
, 6. Which enzyme is responsible for adding N-nucleotides during junctional
diversity of TCR gene rearrangement?
A. RAG-1
B. DNA-PK
C. Terminal deoxynucleotidyl transferase (TdT)
D. Artemis
Answer: C
Rationale: TdT adds non-templated nucleotides (N-nucleotides) to the junctions between
gene segments, increasing diversity.
7. Which molecule functions as a molecular chaperone to stabilize the MHC
Class I heavy chain before beta-2 microglobulin binds?
A. Tapasin
B. Calnexin
C. Calreticulin
D. ERp57
Answer: B
Rationale: Calnexin is the initial chaperone that binds the MHC Class I heavy chain in the
ER.
8. What is the typical length of peptides that bind to MHC Class I molecules?
A. Over 30 amino acids
B. 13-25 amino acids
C. 8-10 amino acids
D. 5-7 amino acids
Answer: C
Rationale: MHC Class I molecules have a closed binding groove that accommodates short
peptides, usually 8 to 10 amino acids long.
