PCB 3233 Final Exam V3 | PCB 3233
Immunology | Actual Q&A with Rationale
(PCB3233 Exam | University of Central
Florida
1. Which of the following molecules is primarily responsible for the presentation of
exogenous antigens to CD4+ T cells?
A. MHC Class I
B. B7-1 (CD80)
C. MHC Class II
D. TCR Gamma-Delta
Answer: C
Rationale: MHC Class II molecules are specialized for the presentation of extracellularly
derived peptides to helper T cells. These molecules are constitutively expressed on
professional antigen-presenting cells like dendritic cells and B cells. The interaction
ensures that the adaptive immune response is directed appropriately toward non-cytosolic
pathogens.
2. The Recombination Activating Gene (RAG) complex is essential for which of the following
processes?
A. Somatic hypermutation
,B. Cytokine signaling
C. Isotype switching
D. V(D)J recombination
Answer: D
Rationale: RAG-1 and RAG-2 proteins are critical components of the recombinase complex
that initiates the assembly of antigen receptor genes. They introduce double-stranded
breaks at recombination signal sequences (RSS) during lymphocyte development. A
deficiency in these enzymes leads to a complete lack of mature B and T cells, resulting in
SCID.
3. Which enzyme is responsible for adding N-nucleotides at the junctions between gene
segments to increase junctional diversity?
A. Activation-induced cytidine deaminase (AID)
B. Artemis
C. DNA Ligase IV
D. Terminal deoxynucleotidyl transferase (TdT)
Answer: D
Rationale: Terminal deoxynucleotidyl transferase (TdT) is a template-independent DNA
polymerase expressed during the early stages of lymphoid development. It randomly adds
, nucleotides to the single-stranded ends of DNA segments after RAG cleavage. This process
significantly expands the repertoire of antigen receptor specificity.
4. In Type I Hypersensitivity, which antibody isotype binds to high-affinity FceRI receptors on
mast cells and basophils?
A. IgG1
B. IgE
C. IgM
D. IgA
Answer: B
Rationale: IgE is the primary antibody involved in allergic reactions and defense against
helminth parasites. Upon first exposure to an allergen, plasma cells produce IgE which then
sensitizes mast cells by binding to their surface receptors. Subsequent exposure leads to
cross-linking and the rapid release of inflammatory mediators like histamine.
5. Which of the following organs is considered a primary lymphoid organ where B cell
maturation occurs in humans?
A. Thymus
B. Spleen
C. Lymph Node
D. Bone Marrow
Immunology | Actual Q&A with Rationale
(PCB3233 Exam | University of Central
Florida
1. Which of the following molecules is primarily responsible for the presentation of
exogenous antigens to CD4+ T cells?
A. MHC Class I
B. B7-1 (CD80)
C. MHC Class II
D. TCR Gamma-Delta
Answer: C
Rationale: MHC Class II molecules are specialized for the presentation of extracellularly
derived peptides to helper T cells. These molecules are constitutively expressed on
professional antigen-presenting cells like dendritic cells and B cells. The interaction
ensures that the adaptive immune response is directed appropriately toward non-cytosolic
pathogens.
2. The Recombination Activating Gene (RAG) complex is essential for which of the following
processes?
A. Somatic hypermutation
,B. Cytokine signaling
C. Isotype switching
D. V(D)J recombination
Answer: D
Rationale: RAG-1 and RAG-2 proteins are critical components of the recombinase complex
that initiates the assembly of antigen receptor genes. They introduce double-stranded
breaks at recombination signal sequences (RSS) during lymphocyte development. A
deficiency in these enzymes leads to a complete lack of mature B and T cells, resulting in
SCID.
3. Which enzyme is responsible for adding N-nucleotides at the junctions between gene
segments to increase junctional diversity?
A. Activation-induced cytidine deaminase (AID)
B. Artemis
C. DNA Ligase IV
D. Terminal deoxynucleotidyl transferase (TdT)
Answer: D
Rationale: Terminal deoxynucleotidyl transferase (TdT) is a template-independent DNA
polymerase expressed during the early stages of lymphoid development. It randomly adds
, nucleotides to the single-stranded ends of DNA segments after RAG cleavage. This process
significantly expands the repertoire of antigen receptor specificity.
4. In Type I Hypersensitivity, which antibody isotype binds to high-affinity FceRI receptors on
mast cells and basophils?
A. IgG1
B. IgE
C. IgM
D. IgA
Answer: B
Rationale: IgE is the primary antibody involved in allergic reactions and defense against
helminth parasites. Upon first exposure to an allergen, plasma cells produce IgE which then
sensitizes mast cells by binding to their surface receptors. Subsequent exposure leads to
cross-linking and the rapid release of inflammatory mediators like histamine.
5. Which of the following organs is considered a primary lymphoid organ where B cell
maturation occurs in humans?
A. Thymus
B. Spleen
C. Lymph Node
D. Bone Marrow
