Immunology Exam 2 (PCB 3233) 2026 – UCF
1. Which molecule is responsible for presenting endogenous antigens to CD8+ T
cells?
A. MHC Class II
B. MHC Class I
C. CD28
D. B7-1
Answer: B
Rationale: MHC Class I molecules present endogenous antigens, typically derived from the
cytosol, to cytotoxic CD8+ T cells.
2. What is the primary function of the Invariant Chain (Ii) in MHC Class II
processing?
A. To degrade viral proteins
B. To transport MHC Class I to the cell surface
C. To activate the TAP transporter
D. To block the peptide-binding groove in the ER
Answer: D
Rationale: The Invariant Chain prevents premature binding of endogenous peptides to
MHC Class II molecules while they are in the endoplasmic reticulum.
,3. Which enzyme is essential for somatic hypermutation and isotype switching
in B cells?
A. RAG-1
B. TdT
C. Artemis
D. AID (Activation-induced cytidine deaminase)
Answer: D
Rationale: AID converts cytosine to uracil in DNA, which is a critical step for both somatic
hypermutation and class-switch recombination.
4. Which cytokine is most associated with the differentiation of Th1 cells?
A. IL-4
B. IL-10
C. IL-12
D. TGF-beta
Answer: C
Rationale: IL-12, often produced by dendritic cells and macrophages, drives the
differentiation of naive T cells into Th1 cells.
5. What is the role of TAP proteins (TAP1 and TAP2) in antigen presentation?
A. Cleaving the leader sequence from the TCR
B. Degrading extracellular proteins
C. Loading peptides onto MHC Class II
D. Transporting peptides from the cytosol into the ER lumen
Answer: D
Rationale: TAP transporters move peptides generated by the proteasome from the cytosol
into the ER for loading onto MHC Class I.
, 6. Positive selection of T cells in the thymus ensures that:
A. T cells recognize self-MHC molecules
B. T cells do not react to self-antigens
C. T cells develop into B cells
D. All T cells survive regardless of TCR specificity
Answer: A
Rationale: Positive selection preserves T cells that have a TCR capable of binding to self-
MHC molecules with moderate affinity.
7. Which of the following is a co-stimulatory signal required for T cell activation?
A. CD40 binding to CD40L
B. CD28 binding to B7 (CD80/86)
C. MHC binding to TCR
D. LFA-1 binding to ICAM-1
Answer: B
Rationale: The interaction between CD28 on the T cell and B7 molecules on the APC is the
secondary signal necessary for full T cell activation.
8. Where does negative selection of thymocytes primarily occur?
A. Thymic medulla
B. Thymic cortex
C. Bone marrow
D. Spleen
Answer: A
Rationale: While some negative selection happens in the cortex, the medulla is the primary
site for deleting self-reactive thymocytes.
1. Which molecule is responsible for presenting endogenous antigens to CD8+ T
cells?
A. MHC Class II
B. MHC Class I
C. CD28
D. B7-1
Answer: B
Rationale: MHC Class I molecules present endogenous antigens, typically derived from the
cytosol, to cytotoxic CD8+ T cells.
2. What is the primary function of the Invariant Chain (Ii) in MHC Class II
processing?
A. To degrade viral proteins
B. To transport MHC Class I to the cell surface
C. To activate the TAP transporter
D. To block the peptide-binding groove in the ER
Answer: D
Rationale: The Invariant Chain prevents premature binding of endogenous peptides to
MHC Class II molecules while they are in the endoplasmic reticulum.
,3. Which enzyme is essential for somatic hypermutation and isotype switching
in B cells?
A. RAG-1
B. TdT
C. Artemis
D. AID (Activation-induced cytidine deaminase)
Answer: D
Rationale: AID converts cytosine to uracil in DNA, which is a critical step for both somatic
hypermutation and class-switch recombination.
4. Which cytokine is most associated with the differentiation of Th1 cells?
A. IL-4
B. IL-10
C. IL-12
D. TGF-beta
Answer: C
Rationale: IL-12, often produced by dendritic cells and macrophages, drives the
differentiation of naive T cells into Th1 cells.
5. What is the role of TAP proteins (TAP1 and TAP2) in antigen presentation?
A. Cleaving the leader sequence from the TCR
B. Degrading extracellular proteins
C. Loading peptides onto MHC Class II
D. Transporting peptides from the cytosol into the ER lumen
Answer: D
Rationale: TAP transporters move peptides generated by the proteasome from the cytosol
into the ER for loading onto MHC Class I.
, 6. Positive selection of T cells in the thymus ensures that:
A. T cells recognize self-MHC molecules
B. T cells do not react to self-antigens
C. T cells develop into B cells
D. All T cells survive regardless of TCR specificity
Answer: A
Rationale: Positive selection preserves T cells that have a TCR capable of binding to self-
MHC molecules with moderate affinity.
7. Which of the following is a co-stimulatory signal required for T cell activation?
A. CD40 binding to CD40L
B. CD28 binding to B7 (CD80/86)
C. MHC binding to TCR
D. LFA-1 binding to ICAM-1
Answer: B
Rationale: The interaction between CD28 on the T cell and B7 molecules on the APC is the
secondary signal necessary for full T cell activation.
8. Where does negative selection of thymocytes primarily occur?
A. Thymic medulla
B. Thymic cortex
C. Bone marrow
D. Spleen
Answer: A
Rationale: While some negative selection happens in the cortex, the medulla is the primary
site for deleting self-reactive thymocytes.
