Immunology Exam 2: PCB 3233 (UCF) 2026 – UCF
1. Which cell type primarily expresses MHC Class II molecules?
A. All nucleated cells
B. Erythrocytes
C. Professional antigen-presenting cells (APCs)
D. Neurons
Answer: C
Rationale: MHC Class II is primarily restricted to professional APCs such as dendritic cells,
macrophages, and B cells, whereas MHC Class I is on almost all nucleated cells.
2. CD8+ T cells are restricted to recognizing antigens presented on which
molecules?
A. MHC Class I
B. MHC Class II
C. CD1
D. Toll-like receptors
Answer: A
Rationale: CD8+ T cells (cytotoxic T cells) recognize endogenous antigens presented on
MHC Class I molecules.
,3. Which molecule is responsible for transporting peptides from the cytosol into
the endoplasmic reticulum for MHC Class I loading?
A. CLIP
B. Invariant chain
C. HLA-DM
D. TAP (Transporter associated with antigen processing)
Answer: D
Rationale: TAP1 and TAP2 form a transporter that moves degraded cytosolic peptides into
the ER lumen to meet MHC Class I molecules.
4. What is the function of the Invariant Chain (Ii) in the MHC Class II pathway?
A. It degrades extracellular proteins.
B. It prevents endogenous peptides from binding to MHC II in the ER.
C. It loads peptides onto MHC I.
D. It acts as a co-receptor for CD8.
Answer: B
Rationale: The invariant chain blocks the peptide-binding groove of MHC Class II in the ER
to prevent it from binding endogenous peptides meant for MHC Class I.
5. Which protein helps remove CLIP from the MHC Class II binding groove to
allow for peptide loading?
A. HLA-DM
B. HLA-DO
C. TAP
D. Calnexin
Answer: A
Rationale: HLA-DM catalyzes the release of CLIP (Class II-associated invariant chain
peptide) so that antigenic peptides can bind to MHC Class II.
, 6. The ‘Endogenous Pathway’ of antigen processing typically leads to
presentation on which molecule?
A. MHC Class II
B. CD4
C. MHC Class I
D. BCR
Answer: C
Rationale: The endogenous pathway processes proteins from within the cell (like viral or
self-proteins) for presentation on MHC Class I.
7. Which enzyme complex is responsible for degrading ubiquitinated proteins in
the cytosol?
A. Lysosome
B. Phagosome
C. Proteasome
D. Endosome
Answer: C
Rationale: The proteasome is a large protein complex that degrades cytosolic proteins into
small peptides for the MHC Class I pathway.
8. The MHC region is highly ‘polymorphic’. What does this mean?
A. There are many different genes for MHC.
B. There are many different alleles for each MHC gene within the population.
C. MHC molecules can change shape once bound to a peptide.
D. MHC genes are only expressed in specific tissues.
Answer: B
Rationale: Polymorphism refers to the existence of multiple alleles for a gene in the
population, which ensures a diverse range of peptide-binding capabilities.
1. Which cell type primarily expresses MHC Class II molecules?
A. All nucleated cells
B. Erythrocytes
C. Professional antigen-presenting cells (APCs)
D. Neurons
Answer: C
Rationale: MHC Class II is primarily restricted to professional APCs such as dendritic cells,
macrophages, and B cells, whereas MHC Class I is on almost all nucleated cells.
2. CD8+ T cells are restricted to recognizing antigens presented on which
molecules?
A. MHC Class I
B. MHC Class II
C. CD1
D. Toll-like receptors
Answer: A
Rationale: CD8+ T cells (cytotoxic T cells) recognize endogenous antigens presented on
MHC Class I molecules.
,3. Which molecule is responsible for transporting peptides from the cytosol into
the endoplasmic reticulum for MHC Class I loading?
A. CLIP
B. Invariant chain
C. HLA-DM
D. TAP (Transporter associated with antigen processing)
Answer: D
Rationale: TAP1 and TAP2 form a transporter that moves degraded cytosolic peptides into
the ER lumen to meet MHC Class I molecules.
4. What is the function of the Invariant Chain (Ii) in the MHC Class II pathway?
A. It degrades extracellular proteins.
B. It prevents endogenous peptides from binding to MHC II in the ER.
C. It loads peptides onto MHC I.
D. It acts as a co-receptor for CD8.
Answer: B
Rationale: The invariant chain blocks the peptide-binding groove of MHC Class II in the ER
to prevent it from binding endogenous peptides meant for MHC Class I.
5. Which protein helps remove CLIP from the MHC Class II binding groove to
allow for peptide loading?
A. HLA-DM
B. HLA-DO
C. TAP
D. Calnexin
Answer: A
Rationale: HLA-DM catalyzes the release of CLIP (Class II-associated invariant chain
peptide) so that antigenic peptides can bind to MHC Class II.
, 6. The ‘Endogenous Pathway’ of antigen processing typically leads to
presentation on which molecule?
A. MHC Class II
B. CD4
C. MHC Class I
D. BCR
Answer: C
Rationale: The endogenous pathway processes proteins from within the cell (like viral or
self-proteins) for presentation on MHC Class I.
7. Which enzyme complex is responsible for degrading ubiquitinated proteins in
the cytosol?
A. Lysosome
B. Phagosome
C. Proteasome
D. Endosome
Answer: C
Rationale: The proteasome is a large protein complex that degrades cytosolic proteins into
small peptides for the MHC Class I pathway.
8. The MHC region is highly ‘polymorphic’. What does this mean?
A. There are many different genes for MHC.
B. There are many different alleles for each MHC gene within the population.
C. MHC molecules can change shape once bound to a peptide.
D. MHC genes are only expressed in specific tissues.
Answer: B
Rationale: Polymorphism refers to the existence of multiple alleles for a gene in the
population, which ensures a diverse range of peptide-binding capabilities.
