Immunology Exam 3: Chapters 5 & 6 2026 – UCF
1. Which of the following molecules is NOT part of the MHC Class I heterodimer?
A. Alpha-1 domain
B. Alpha-2 domain
C. Invariant chain
D. Beta-2 microglobulin
Answer: C
Rationale: The Invariant chain (Ii) is associated with MHC Class II in the endoplasmic
reticulum, not MHC Class I.
2. MHC Class II molecules primarily present peptides derived from which
source?
A. Cytosolic proteins
B. Nuclear proteins
C. Extracellular pathogens
D. Mitochondrial proteins
Answer: C
Rationale: MHC Class II molecules present peptides from the endocytic pathway, which
usually involves extracellular pathogens.
,3. Which enzyme is responsible for degrading cytosolic proteins into peptides
for MHC Class I presentation?
A. Proteasome
B. Cathepsin
C. TdT
D. RAG-1
Answer: A
Rationale: The proteasome is a multi-catalytic protease complex that degrades cytosolic
proteins for MHC Class I presentation.
4. The peptide-binding groove of MHC Class I is formed by which domains?
A. Alpha-3 and Beta-2 microglobulin
B. Alpha-1 and Beta-1
C. Alpha-2 and Beta-2
D. Alpha-1 and Alpha-2
Answer: D
Rationale: The alpha-1 and alpha-2 domains of the MHC Class I heavy chain fold together
to form the peptide-binding cleft.
5. Which protein transports peptides from the cytosol into the lumen of the
endoplasmic reticulum?
A. TAP1/2
B. Calnexin
C. HLA-DM
D. CLIP
Answer: A
Rationale: TAP (Transporter associated with antigen processing) 1 and 2 move peptides
across the ER membrane.
, 6. What is the typical length of a peptide that binds to an MHC Class I molecule?
A. 5-7 amino acids
B. 30-50 amino acids
C. 13-25 amino acids
D. 8-10 amino acids
Answer: D
Rationale: MHC Class I molecules typically bind short peptides of 8 to 10 amino acids in
length.
7. Which molecule facilitates the removal of CLIP from MHC Class II molecules?
A. HLA-DM
B. TAP
C. HLA-DO
D. Calreticulin
Answer: A
Rationale: HLA-DM catalyzes the release of CLIP and allows the loading of other peptides
into the MHC Class II groove.
8. In the context of MHC genetics, what does ‘polymorphism’ refer to?
A. The presence of multiple genes for MHC Class I and II
B. The expression of both maternal and paternal alleles
C. The existence of many different alleles for a gene within the population
D. The ability of one MHC molecule to bind many different peptides
Answer: C
Rationale: Polymorphism refers to the high degree of variation in MHC alleles across the
population.
1. Which of the following molecules is NOT part of the MHC Class I heterodimer?
A. Alpha-1 domain
B. Alpha-2 domain
C. Invariant chain
D. Beta-2 microglobulin
Answer: C
Rationale: The Invariant chain (Ii) is associated with MHC Class II in the endoplasmic
reticulum, not MHC Class I.
2. MHC Class II molecules primarily present peptides derived from which
source?
A. Cytosolic proteins
B. Nuclear proteins
C. Extracellular pathogens
D. Mitochondrial proteins
Answer: C
Rationale: MHC Class II molecules present peptides from the endocytic pathway, which
usually involves extracellular pathogens.
,3. Which enzyme is responsible for degrading cytosolic proteins into peptides
for MHC Class I presentation?
A. Proteasome
B. Cathepsin
C. TdT
D. RAG-1
Answer: A
Rationale: The proteasome is a multi-catalytic protease complex that degrades cytosolic
proteins for MHC Class I presentation.
4. The peptide-binding groove of MHC Class I is formed by which domains?
A. Alpha-3 and Beta-2 microglobulin
B. Alpha-1 and Beta-1
C. Alpha-2 and Beta-2
D. Alpha-1 and Alpha-2
Answer: D
Rationale: The alpha-1 and alpha-2 domains of the MHC Class I heavy chain fold together
to form the peptide-binding cleft.
5. Which protein transports peptides from the cytosol into the lumen of the
endoplasmic reticulum?
A. TAP1/2
B. Calnexin
C. HLA-DM
D. CLIP
Answer: A
Rationale: TAP (Transporter associated with antigen processing) 1 and 2 move peptides
across the ER membrane.
, 6. What is the typical length of a peptide that binds to an MHC Class I molecule?
A. 5-7 amino acids
B. 30-50 amino acids
C. 13-25 amino acids
D. 8-10 amino acids
Answer: D
Rationale: MHC Class I molecules typically bind short peptides of 8 to 10 amino acids in
length.
7. Which molecule facilitates the removal of CLIP from MHC Class II molecules?
A. HLA-DM
B. TAP
C. HLA-DO
D. Calreticulin
Answer: A
Rationale: HLA-DM catalyzes the release of CLIP and allows the loading of other peptides
into the MHC Class II groove.
8. In the context of MHC genetics, what does ‘polymorphism’ refer to?
A. The presence of multiple genes for MHC Class I and II
B. The expression of both maternal and paternal alleles
C. The existence of many different alleles for a gene within the population
D. The ability of one MHC molecule to bind many different peptides
Answer: C
Rationale: Polymorphism refers to the high degree of variation in MHC alleles across the
population.
