PCB 3233 Exam 2 V3 | PCB 3233
Immunology | Actual Q&A with Rationale
(PCB3233 Exam 2) | University of Central
Florida
1. Which molecule is responsible for the removal of the CLIP peptide from MHC class II
molecules in the MIIC compartment?
A. HLA-DM
B. Calreticulin
C. Invariant Chain
D. TAP1/2
Answer: A
Rationale: HLA-DM acts as a catalyst that facilitates the release of the Class II-associated
invariant chain peptide (CLIP) from the MHC class II binding groove. This allows higher-
affinity antigenic peptides to bind before the complex is transported to the cell surface.
This process is essential for the proper presentation of exogenous antigens to CD4 T cells.
2. The pre-B cell receptor is composed of a functional mu heavy chain and which of the
following?
A. Ig-alpha and Ig-beta alone
B. Kappa light chain
,C. Lambda light chain
D. Surrogate light chain (VpreB and lambda-5)
Answer: D
Rationale: During the pre-B cell stage, the successfully rearranged heavy chain pairs with a
surrogate light chain to form the pre-B cell receptor. This complex signals the cell to stop
further heavy chain rearrangement and begin proliferating. It serves as the first major
checkpoint in B-cell development to ensure a functional heavy chain has been produced.
3. In which stage of T-cell development does the cell first express both CD4 and CD8 co-
receptors?
A. Double-negative (DN) stage
B. Double-positive (DP) stage
C. Single-positive (SP) stage
D. Pro-T cell stage
Answer: B
Rationale: The double-positive stage occurs in the thymic cortex after the successful
rearrangement of the TCR beta chain. During this phase, thymocytes express both CD4 and
CD8 and undergo the critical process of positive selection. Failure to interact with MHC
molecules during this stage results in death by neglect.
, 4. Which enzyme is responsible for adding N-nucleotides during junctional diversity to
increase the repertoire of receptors?
A. RAG-1/2
B. Terminal deoxynucleotidyl transferase (TdT)
C. Artemis
D. DNA Ligase IV
Answer: B
Rationale: Terminal deoxynucleotidyl transferase (TdT) is a specialized DNA polymerase
that adds non-templated nucleotides to the V, D, and J junctions. This process significantly
increases the diversity of both B-cell and T-cell receptors beyond what is encoded in the
germline. TdT is primarily active during heavy chain rearrangement in B cells and all TCR
chain rearrangements.
5. MHC Class I molecules primarily present peptides derived from which cellular
compartment?
A. Extracellular space
B. Endosomes
C. Cytosol
D. Lysosomes
Answer: C
Immunology | Actual Q&A with Rationale
(PCB3233 Exam 2) | University of Central
Florida
1. Which molecule is responsible for the removal of the CLIP peptide from MHC class II
molecules in the MIIC compartment?
A. HLA-DM
B. Calreticulin
C. Invariant Chain
D. TAP1/2
Answer: A
Rationale: HLA-DM acts as a catalyst that facilitates the release of the Class II-associated
invariant chain peptide (CLIP) from the MHC class II binding groove. This allows higher-
affinity antigenic peptides to bind before the complex is transported to the cell surface.
This process is essential for the proper presentation of exogenous antigens to CD4 T cells.
2. The pre-B cell receptor is composed of a functional mu heavy chain and which of the
following?
A. Ig-alpha and Ig-beta alone
B. Kappa light chain
,C. Lambda light chain
D. Surrogate light chain (VpreB and lambda-5)
Answer: D
Rationale: During the pre-B cell stage, the successfully rearranged heavy chain pairs with a
surrogate light chain to form the pre-B cell receptor. This complex signals the cell to stop
further heavy chain rearrangement and begin proliferating. It serves as the first major
checkpoint in B-cell development to ensure a functional heavy chain has been produced.
3. In which stage of T-cell development does the cell first express both CD4 and CD8 co-
receptors?
A. Double-negative (DN) stage
B. Double-positive (DP) stage
C. Single-positive (SP) stage
D. Pro-T cell stage
Answer: B
Rationale: The double-positive stage occurs in the thymic cortex after the successful
rearrangement of the TCR beta chain. During this phase, thymocytes express both CD4 and
CD8 and undergo the critical process of positive selection. Failure to interact with MHC
molecules during this stage results in death by neglect.
, 4. Which enzyme is responsible for adding N-nucleotides during junctional diversity to
increase the repertoire of receptors?
A. RAG-1/2
B. Terminal deoxynucleotidyl transferase (TdT)
C. Artemis
D. DNA Ligase IV
Answer: B
Rationale: Terminal deoxynucleotidyl transferase (TdT) is a specialized DNA polymerase
that adds non-templated nucleotides to the V, D, and J junctions. This process significantly
increases the diversity of both B-cell and T-cell receptors beyond what is encoded in the
germline. TdT is primarily active during heavy chain rearrangement in B cells and all TCR
chain rearrangements.
5. MHC Class I molecules primarily present peptides derived from which cellular
compartment?
A. Extracellular space
B. Endosomes
C. Cytosol
D. Lysosomes
Answer: C
