PCB 3233 Immunology Exam 2: Adaptive Immunity, MHC, and
Lymphocyte Development 2026 – UCF
1. Which molecule is responsible for transporting peptides from the cytosol into
the lumen of the endoplasmic reticulum (ER) for MHC Class I loading?
A. Calnexin
B. HLA-DM
C. Invariant chain (Ii)
D. TAP (Transporter associated with antigen processing)
Answer: D
Rationale: TAP is a heterodimer in the ER membrane that pumps degraded cytosolic
peptides into the ER lumen to be loaded onto MHC Class I molecules.
2. In the exogenous pathway of antigen processing, what is the role of the
invariant chain (Ii)?
A. It blocks the peptide-binding groove of MHC Class II in the ER.
B. It functions as a chaperone for TCR assembly.
C. It stabilizes MHC Class I until a peptide binds.
D. It degrades misfolded proteins in the proteasome.
Answer: A
Rationale: The invariant chain prevents MHC Class II from binding endogenous peptides in
the ER, ensuring it only binds exogenous peptides in the endosomal compartment.
,3. Which of the following is a characteristic of MHC Class I molecules?
A. Consists of an alpha chain and a non-covalently associated beta-2 microglobulin.
B. Presents peptides derived from extracellular pathogens.
C. Expressed only on professional antigen-presenting cells.
D. Consists of two transmembrane chains, alpha and beta.
Answer: A
Rationale: MHC Class I is composed of one polymorphic alpha chain and a constant beta-2
microglobulin molecule.
4. Cross-presentation is a unique process primarily carried out by which cell
type?
A. B cells
B. Dendritic cells
C. Neutrophils
D. Erythrocytes
Answer: B
Rationale: Dendritic cells have the unique ability to take up exogenous antigens and
present them on MHC Class I molecules to activate CD8+ T cells.
5. MHC Class II molecules typically present peptides that are how many amino
acids in length?
A. 13-25 amino acids
B. 8-10 amino acids
C. Exactly 9 amino acids
D. Over 50 amino acids
Answer: A
Rationale: MHC Class II has an open-ended binding groove, allowing it to accommodate
longer peptides, usually between 13 and 25 amino acids.
, 6. Which enzyme is responsible for the degradation of proteins into peptides for
the MHC Class I pathway?
A. TdT
B. Cathepsin
C. Lysozyme
D. Proteasome
Answer: D
Rationale: The proteasome is a multicatalytic protease complex that degrades cytosolic
proteins into peptides for MHC I presentation.
7. The process by which T cells that recognize self-MHC molecules are selected
to survive is called:
A. Negative selection
B. Clonal anergy
C. Positive selection
D. Receptor editing
Answer: C
Rationale: Positive selection occurs in the thymic cortex and ensures that T cells have a
TCR capable of interacting with the individual’s self-MHC molecules.
8. Which signaling molecule is essential for driving a lymphoid progenitor to
become a T cell rather than a B cell?
A. Notch-1
B. Pax-5
C. EBF
D. PU.1
Answer: A
Rationale: Notch-1 signaling in the thymus is the ‘master regulator’ that commits
lymphoid progenitors to the T-cell lineage.
Lymphocyte Development 2026 – UCF
1. Which molecule is responsible for transporting peptides from the cytosol into
the lumen of the endoplasmic reticulum (ER) for MHC Class I loading?
A. Calnexin
B. HLA-DM
C. Invariant chain (Ii)
D. TAP (Transporter associated with antigen processing)
Answer: D
Rationale: TAP is a heterodimer in the ER membrane that pumps degraded cytosolic
peptides into the ER lumen to be loaded onto MHC Class I molecules.
2. In the exogenous pathway of antigen processing, what is the role of the
invariant chain (Ii)?
A. It blocks the peptide-binding groove of MHC Class II in the ER.
B. It functions as a chaperone for TCR assembly.
C. It stabilizes MHC Class I until a peptide binds.
D. It degrades misfolded proteins in the proteasome.
Answer: A
Rationale: The invariant chain prevents MHC Class II from binding endogenous peptides in
the ER, ensuring it only binds exogenous peptides in the endosomal compartment.
,3. Which of the following is a characteristic of MHC Class I molecules?
A. Consists of an alpha chain and a non-covalently associated beta-2 microglobulin.
B. Presents peptides derived from extracellular pathogens.
C. Expressed only on professional antigen-presenting cells.
D. Consists of two transmembrane chains, alpha and beta.
Answer: A
Rationale: MHC Class I is composed of one polymorphic alpha chain and a constant beta-2
microglobulin molecule.
4. Cross-presentation is a unique process primarily carried out by which cell
type?
A. B cells
B. Dendritic cells
C. Neutrophils
D. Erythrocytes
Answer: B
Rationale: Dendritic cells have the unique ability to take up exogenous antigens and
present them on MHC Class I molecules to activate CD8+ T cells.
5. MHC Class II molecules typically present peptides that are how many amino
acids in length?
A. 13-25 amino acids
B. 8-10 amino acids
C. Exactly 9 amino acids
D. Over 50 amino acids
Answer: A
Rationale: MHC Class II has an open-ended binding groove, allowing it to accommodate
longer peptides, usually between 13 and 25 amino acids.
, 6. Which enzyme is responsible for the degradation of proteins into peptides for
the MHC Class I pathway?
A. TdT
B. Cathepsin
C. Lysozyme
D. Proteasome
Answer: D
Rationale: The proteasome is a multicatalytic protease complex that degrades cytosolic
proteins into peptides for MHC I presentation.
7. The process by which T cells that recognize self-MHC molecules are selected
to survive is called:
A. Negative selection
B. Clonal anergy
C. Positive selection
D. Receptor editing
Answer: C
Rationale: Positive selection occurs in the thymic cortex and ensures that T cells have a
TCR capable of interacting with the individual’s self-MHC molecules.
8. Which signaling molecule is essential for driving a lymphoid progenitor to
become a T cell rather than a B cell?
A. Notch-1
B. Pax-5
C. EBF
D. PU.1
Answer: A
Rationale: Notch-1 signaling in the thymus is the ‘master regulator’ that commits
lymphoid progenitors to the T-cell lineage.
