PCB 3233 Exam 4 V2 | PCB 3233 Immunology |
Actual Q&A with Rationale (PCB3233 Exam 4) |
University of Central Florida
1. Which immunoglobulin isotype is primarily responsible for mediating Type I
hypersensitivity reactions?
A. IgG
B. IgM
C. IgE
D. IgD
Correct Answer: C
Explanation: Type I hypersensitivity is mediated by IgE antibodies that bind to high-
affinity Fc epsilon receptors on mast cells and basophils. Upon subsequent exposure to an
allergen, cross-linking of these IgE molecules triggers the release of inflammatory
mediators like histamine. This reaction is responsible for common allergies, asthma, and
systemic anaphylaxis.
2. In Type II hypersensitivity, the mechanism of tissue damage involves which of the
following?
A. Immune complex deposition in blood vessel walls
B. Antibody-mediated cell lysis via complement activation
,C. Delayed-type T-cell activation
D. Release of histamine from mast cells
Correct Answer: B
Explanation: Type II hypersensitivity involves IgG or IgM antibodies binding directly to
antigens on the surface of host cells. This binding can lead to cell destruction through the
classical complement pathway or antibody-dependent cellular cytotoxicity (ADCC). Clinical
examples include mismatched blood transfusions and hemolytic disease of the newborn.
3. Systemic Lupus Erythematosus (SLE) is characterized by the production of antibodies
against:
A. Double-stranded DNA and other nuclear antigens
B. Acetylcholine receptors
C. Thyroid-stimulating hormone receptors
D. Myelin basic protein
Correct Answer: A
Explanation: SLE is a systemic autoimmune disease characterized by a loss of tolerance to
self-antigens, particularly nuclear components. The presence of anti-nuclear antibodies
(ANAs) is a hallmark diagnostic feature used by clinicians. These immune complexes
deposit in various organs, leading to widespread inflammation and tissue damage.
, 4. Which of the following describes the mechanism of Myasthenia Gravis?
A. Destruction of pancreatic beta cells
B. T-cell mediated destruction of the myelin sheath
C. Antibodies blocking acetylcholine receptors at the neuromuscular junction
D. Overstimulation of the thyroid gland by antibodies
Correct Answer: C
Explanation: Myasthenia Gravis is an organ-specific autoimmune disease where
autoantibodies target the nicotinic acetylcholine receptors. These antibodies block the
binding of acetylcholine and lead to the internalisation and degradation of the receptors.
The resulting impairment in neuromuscular transmission causes progressive muscle
weakness and fatigue.
5. A 25-year-old patient presents with a skin rash 48 hours after contact with poison ivy. This
is an example of which hypersensitivity?
A. Type IV
B. Type II
C. Type III
D. Type I
Correct Answer: A
Actual Q&A with Rationale (PCB3233 Exam 4) |
University of Central Florida
1. Which immunoglobulin isotype is primarily responsible for mediating Type I
hypersensitivity reactions?
A. IgG
B. IgM
C. IgE
D. IgD
Correct Answer: C
Explanation: Type I hypersensitivity is mediated by IgE antibodies that bind to high-
affinity Fc epsilon receptors on mast cells and basophils. Upon subsequent exposure to an
allergen, cross-linking of these IgE molecules triggers the release of inflammatory
mediators like histamine. This reaction is responsible for common allergies, asthma, and
systemic anaphylaxis.
2. In Type II hypersensitivity, the mechanism of tissue damage involves which of the
following?
A. Immune complex deposition in blood vessel walls
B. Antibody-mediated cell lysis via complement activation
,C. Delayed-type T-cell activation
D. Release of histamine from mast cells
Correct Answer: B
Explanation: Type II hypersensitivity involves IgG or IgM antibodies binding directly to
antigens on the surface of host cells. This binding can lead to cell destruction through the
classical complement pathway or antibody-dependent cellular cytotoxicity (ADCC). Clinical
examples include mismatched blood transfusions and hemolytic disease of the newborn.
3. Systemic Lupus Erythematosus (SLE) is characterized by the production of antibodies
against:
A. Double-stranded DNA and other nuclear antigens
B. Acetylcholine receptors
C. Thyroid-stimulating hormone receptors
D. Myelin basic protein
Correct Answer: A
Explanation: SLE is a systemic autoimmune disease characterized by a loss of tolerance to
self-antigens, particularly nuclear components. The presence of anti-nuclear antibodies
(ANAs) is a hallmark diagnostic feature used by clinicians. These immune complexes
deposit in various organs, leading to widespread inflammation and tissue damage.
, 4. Which of the following describes the mechanism of Myasthenia Gravis?
A. Destruction of pancreatic beta cells
B. T-cell mediated destruction of the myelin sheath
C. Antibodies blocking acetylcholine receptors at the neuromuscular junction
D. Overstimulation of the thyroid gland by antibodies
Correct Answer: C
Explanation: Myasthenia Gravis is an organ-specific autoimmune disease where
autoantibodies target the nicotinic acetylcholine receptors. These antibodies block the
binding of acetylcholine and lead to the internalisation and degradation of the receptors.
The resulting impairment in neuromuscular transmission causes progressive muscle
weakness and fatigue.
5. A 25-year-old patient presents with a skin rash 48 hours after contact with poison ivy. This
is an example of which hypersensitivity?
A. Type IV
B. Type II
C. Type III
D. Type I
Correct Answer: A
