PCB 3233 Exam 4 V3 | PCB 3233 Immunology |
Actual Q&A with Rationale (PCB3233 Exam 4) |
University of Central Florida
1. Which of the following mediators is primarily responsible for the immediate vasodilation
and increased vascular permeability seen in Type I hypersensitivity?
A. Leukotrienes
B. Histamine
C. Prostaglandins
D. Cytokines
Correct Answer: B
Explanation: Histamine is pre-formed and stored in mast cell granules, allowing for near-
instantaneous release upon IgE-mediated activation. It acts quickly on H1 receptors to
cause smooth muscle contraction and vascular leakage. This rapid response distinguishes
the immediate phase from the late-phase reaction mediated by newly synthesized lipids.
2. In the context of central tolerance, what is the primary role of the Autoimmune Regulator
(AIRE) protein?
A. Promoting the differentiation of Th17 cells
B. Inducing expression of tissue-specific antigens in the thymus
C. Mediating the isotype switching of B cells
,D. Activating the complement classical pathway
Correct Answer: B
Explanation: AIRE is a transcription factor expressed in medullary thymic epithelial cells
that allows for the expression of proteins usually found only in peripheral tissues. This
enables the screening of developing T cells against a wide array of self-antigens during
negative selection. Defects in the AIRE gene lead to multi-organ autoimmune diseases like
APECED.
3. A patient presents with butterfly-shaped facial rash and high titers of anti-nuclear
antibodies (ANA). Which type of hypersensitivity is most characteristic of this condition?
A. Type I
B. Type II
C. Type IV
D. Type III
Correct Answer: D
Explanation: Systemic Lupus Erythematosus (SLE) is the classic example of a Type III
hypersensitivity reaction involving immune complex deposition. These complexes of DNA
and anti-DNA antibodies lodge in small vessels, causing glomerulonephritis, vasculitis, and
arthritis. The subsequent activation of complement leads to significant tissue damage and
inflammation.
, 4. Delayed-type hypersensitivity (DTH) reactions, such as the tuberculin skin test, are
primarily mediated by which cell type?
A. B lymphocytes
B. Th1 cells
C. Mast cells
D. Eosinophils
Correct Answer: B
Explanation: Type IV hypersensitivity is a cell-mediated response that typically takes 24-
72 hours to develop. Th1 cells recognize the antigen and release cytokines like IFN-gamma
to recruit and activate macrophages. This process causes the characteristic induration and
inflammation associated with DTH reactions.
5. Which pharmacological agent functions by inhibiting calcineurin, thereby preventing the
transcription of IL-2 in T cells?
A. Azathioprine
B. Methotrexate
C. Cyclosporine
D. Rituximab
Correct Answer: C
Actual Q&A with Rationale (PCB3233 Exam 4) |
University of Central Florida
1. Which of the following mediators is primarily responsible for the immediate vasodilation
and increased vascular permeability seen in Type I hypersensitivity?
A. Leukotrienes
B. Histamine
C. Prostaglandins
D. Cytokines
Correct Answer: B
Explanation: Histamine is pre-formed and stored in mast cell granules, allowing for near-
instantaneous release upon IgE-mediated activation. It acts quickly on H1 receptors to
cause smooth muscle contraction and vascular leakage. This rapid response distinguishes
the immediate phase from the late-phase reaction mediated by newly synthesized lipids.
2. In the context of central tolerance, what is the primary role of the Autoimmune Regulator
(AIRE) protein?
A. Promoting the differentiation of Th17 cells
B. Inducing expression of tissue-specific antigens in the thymus
C. Mediating the isotype switching of B cells
,D. Activating the complement classical pathway
Correct Answer: B
Explanation: AIRE is a transcription factor expressed in medullary thymic epithelial cells
that allows for the expression of proteins usually found only in peripheral tissues. This
enables the screening of developing T cells against a wide array of self-antigens during
negative selection. Defects in the AIRE gene lead to multi-organ autoimmune diseases like
APECED.
3. A patient presents with butterfly-shaped facial rash and high titers of anti-nuclear
antibodies (ANA). Which type of hypersensitivity is most characteristic of this condition?
A. Type I
B. Type II
C. Type IV
D. Type III
Correct Answer: D
Explanation: Systemic Lupus Erythematosus (SLE) is the classic example of a Type III
hypersensitivity reaction involving immune complex deposition. These complexes of DNA
and anti-DNA antibodies lodge in small vessels, causing glomerulonephritis, vasculitis, and
arthritis. The subsequent activation of complement leads to significant tissue damage and
inflammation.
, 4. Delayed-type hypersensitivity (DTH) reactions, such as the tuberculin skin test, are
primarily mediated by which cell type?
A. B lymphocytes
B. Th1 cells
C. Mast cells
D. Eosinophils
Correct Answer: B
Explanation: Type IV hypersensitivity is a cell-mediated response that typically takes 24-
72 hours to develop. Th1 cells recognize the antigen and release cytokines like IFN-gamma
to recruit and activate macrophages. This process causes the characteristic induration and
inflammation associated with DTH reactions.
5. Which pharmacological agent functions by inhibiting calcineurin, thereby preventing the
transcription of IL-2 in T cells?
A. Azathioprine
B. Methotrexate
C. Cyclosporine
D. Rituximab
Correct Answer: C
