Immunology Exam 2 - PCB 3233 2026 – UCF
1. Which molecule is responsible for transporting peptides from the cytosol into
the endoplasmic reticulum for loading onto MHC Class I?
A. Calnexin
B. CLIP
C. Invariant chain
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 meet MHC Class I molecules.
2. Where does the negative selection of B cells primarily occur?
A. Bone Marrow
B. Spleen
C. Thymus
D. Lymph Nodes
Answer: A
Rationale: B cell negative selection occurs in the bone marrow where self-reactive B cells
are eliminated or undergo receptor editing.
,3. Which isotype is the first to be produced by a B cell during a primary immune
response?
A. IgG
B. IgA
C. IgM
D. IgE
Answer: C
Rationale: IgM is the default isotype expressed by naive B cells and the first secreted
antibody in a primary response before class switching occurs.
4. Which T cell subset is primarily responsible for activating macrophages to kill
intracellular pathogens?
A. Treg
B. TH2
C. TH17
D. TH1
Answer: D
Rationale: TH1 cells secrete IFN-gamma and express CD40 ligand, which are critical
signals for macrophage activation.
5. The process of ‘Somatic Hypermutation’ occurs in which location?
A. Thymic cortex
B. Bloodstream
C. Bone marrow niche
D. Germinal centers of secondary lymphoid organs
Answer: D
Rationale: Somatic hypermutation occurs in B cells within the germinal centers after they
have been activated by antigen and T cell help.
, 6. Which MHC molecule presents antigens derived from extracellular pathogens
that have been endocytosed?
A. MHC Class I
B. CD1
C. MHC Class III
D. MHC Class II
Answer: D
Rationale: MHC Class II molecules present exogenous antigens that are internalized into
endosomes/lysosomes by professional APCs.
7. What is the function of the Invariant Chain (Ii) in the MHC II pathway?
A. To degrade intracellular proteins
B. To block the peptide-binding groove of MHC II in the ER
C. To transport peptides into the ER
D. To activate CD8 T cells
Answer: B
Rationale: The Invariant Chain prevents MHC II from binding endogenous peptides in the
ER, ensuring it only binds exogenous peptides in the MIIC compartment.
8. Which cytokine is essential for the differentiation of naive T cells into TH2
cells?
A. IL-4
B. IFN-gamma
C. IL-12
D. TGF-beta
Answer: A
Rationale: IL-4 induces the transcription factor GATA3, driving the differentiation of CD4 T
cells toward the TH2 lineage.
1. Which molecule is responsible for transporting peptides from the cytosol into
the endoplasmic reticulum for loading onto MHC Class I?
A. Calnexin
B. CLIP
C. Invariant chain
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 meet MHC Class I molecules.
2. Where does the negative selection of B cells primarily occur?
A. Bone Marrow
B. Spleen
C. Thymus
D. Lymph Nodes
Answer: A
Rationale: B cell negative selection occurs in the bone marrow where self-reactive B cells
are eliminated or undergo receptor editing.
,3. Which isotype is the first to be produced by a B cell during a primary immune
response?
A. IgG
B. IgA
C. IgM
D. IgE
Answer: C
Rationale: IgM is the default isotype expressed by naive B cells and the first secreted
antibody in a primary response before class switching occurs.
4. Which T cell subset is primarily responsible for activating macrophages to kill
intracellular pathogens?
A. Treg
B. TH2
C. TH17
D. TH1
Answer: D
Rationale: TH1 cells secrete IFN-gamma and express CD40 ligand, which are critical
signals for macrophage activation.
5. The process of ‘Somatic Hypermutation’ occurs in which location?
A. Thymic cortex
B. Bloodstream
C. Bone marrow niche
D. Germinal centers of secondary lymphoid organs
Answer: D
Rationale: Somatic hypermutation occurs in B cells within the germinal centers after they
have been activated by antigen and T cell help.
, 6. Which MHC molecule presents antigens derived from extracellular pathogens
that have been endocytosed?
A. MHC Class I
B. CD1
C. MHC Class III
D. MHC Class II
Answer: D
Rationale: MHC Class II molecules present exogenous antigens that are internalized into
endosomes/lysosomes by professional APCs.
7. What is the function of the Invariant Chain (Ii) in the MHC II pathway?
A. To degrade intracellular proteins
B. To block the peptide-binding groove of MHC II in the ER
C. To transport peptides into the ER
D. To activate CD8 T cells
Answer: B
Rationale: The Invariant Chain prevents MHC II from binding endogenous peptides in the
ER, ensuring it only binds exogenous peptides in the MIIC compartment.
8. Which cytokine is essential for the differentiation of naive T cells into TH2
cells?
A. IL-4
B. IFN-gamma
C. IL-12
D. TGF-beta
Answer: A
Rationale: IL-4 induces the transcription factor GATA3, driving the differentiation of CD4 T
cells toward the TH2 lineage.
