PCB 3233 Final Exam V2 | PCB 3233 Immunology |
Actual Q&A with Rationale (PCB3233 Final Exam) |
University of Central Florida
1. Which molecule is responsible for the transport of exogenous antigens into the MHC Class
II pathway?
A. TAP1/TAP2 transporter
B. Ubiquitin
C. Calnexin
D. Invariant chain (Ii)
Correct Answer: D
Explanation: The invariant chain (Ii) blocks the peptide-binding groove of MHC Class II in
the endoplasmic reticulum to prevent premature binding of endogenous peptides. It also
contains sequences that direct the MHC Class II molecule to the endosomal compartment
for antigen loading. This mechanism is critical for ensuring that MHC II specifically presents
exogenous antigens derived from the extracellular environment.
2. Which of the following antibody isotypes is primarily associated with mucosal immunity
and exists as a dimer in secretions?
A. IgA
B. IgE
,C. IgG
D. IgD
Correct Answer: A
Explanation: IgA is the predominant antibody found in mucosal secretions such as saliva,
tears, and breast milk. In these environments, it typically forms a dimer held together by a J
chain and a secretory component. This structural configuration allows IgA to effectively
neutralize pathogens at the body’s points of entry before they can penetrate deeper tissues.
3. In the process of T-cell development, what is the result of a thymocyte binding with high
affinity to self-peptide:MHC complexes?
A. Negative selection (Apoptosis)
B. Positive selection
C. Lineage commitment to CD8
D. Proliferation
Correct Answer: A
Explanation: Negative selection occurs in the thymus when thymocytes bind too strongly
to self-antigen:MHC complexes presented by medullary epithelial cells or dendritic cells.
This process triggers apoptosis to eliminate potentially autoreactive T cells from the
repertoire. It is a fundamental mechanism of central tolerance that prevents the
development of autoimmune diseases.
, 4. Which complement component is known as the ‘potent anaphylatoxin’ and also serves as a
chemoattractant for neutrophils?
A. C5a
B. C3b
C. C9
D. C1q
Correct Answer: A
Explanation: C5a is a powerful bioactive fragment produced during the cleavage of C5 by
C5 convertase. It functions as an anaphylatoxin by inducing mast cell degranulation and
increases vascular permeability. Furthermore, it acts as a potent chemoattractant that
recruits neutrophils and monocytes to the site of infection or inflammation.
5. What is the primary role of the RAG-1 and RAG-2 enzymes in lymphocyte development?
A. Somatic hypermutation
B. Class switch recombination
C. Affinity maturation
D. V(D)J recombination
Correct Answer: D
Explanation: RAG-1 and RAG-2 are essential recombinases that initiate the process of
V(D)J recombination in developing B and T cells. They recognize recombination signal
Actual Q&A with Rationale (PCB3233 Final Exam) |
University of Central Florida
1. Which molecule is responsible for the transport of exogenous antigens into the MHC Class
II pathway?
A. TAP1/TAP2 transporter
B. Ubiquitin
C. Calnexin
D. Invariant chain (Ii)
Correct Answer: D
Explanation: The invariant chain (Ii) blocks the peptide-binding groove of MHC Class II in
the endoplasmic reticulum to prevent premature binding of endogenous peptides. It also
contains sequences that direct the MHC Class II molecule to the endosomal compartment
for antigen loading. This mechanism is critical for ensuring that MHC II specifically presents
exogenous antigens derived from the extracellular environment.
2. Which of the following antibody isotypes is primarily associated with mucosal immunity
and exists as a dimer in secretions?
A. IgA
B. IgE
,C. IgG
D. IgD
Correct Answer: A
Explanation: IgA is the predominant antibody found in mucosal secretions such as saliva,
tears, and breast milk. In these environments, it typically forms a dimer held together by a J
chain and a secretory component. This structural configuration allows IgA to effectively
neutralize pathogens at the body’s points of entry before they can penetrate deeper tissues.
3. In the process of T-cell development, what is the result of a thymocyte binding with high
affinity to self-peptide:MHC complexes?
A. Negative selection (Apoptosis)
B. Positive selection
C. Lineage commitment to CD8
D. Proliferation
Correct Answer: A
Explanation: Negative selection occurs in the thymus when thymocytes bind too strongly
to self-antigen:MHC complexes presented by medullary epithelial cells or dendritic cells.
This process triggers apoptosis to eliminate potentially autoreactive T cells from the
repertoire. It is a fundamental mechanism of central tolerance that prevents the
development of autoimmune diseases.
, 4. Which complement component is known as the ‘potent anaphylatoxin’ and also serves as a
chemoattractant for neutrophils?
A. C5a
B. C3b
C. C9
D. C1q
Correct Answer: A
Explanation: C5a is a powerful bioactive fragment produced during the cleavage of C5 by
C5 convertase. It functions as an anaphylatoxin by inducing mast cell degranulation and
increases vascular permeability. Furthermore, it acts as a potent chemoattractant that
recruits neutrophils and monocytes to the site of infection or inflammation.
5. What is the primary role of the RAG-1 and RAG-2 enzymes in lymphocyte development?
A. Somatic hypermutation
B. Class switch recombination
C. Affinity maturation
D. V(D)J recombination
Correct Answer: D
Explanation: RAG-1 and RAG-2 are essential recombinases that initiate the process of
V(D)J recombination in developing B and T cells. They recognize recombination signal
