PCB 3233 Exam 4 V1| PCB 3233 Immunology |
Actual Q&A with Rationale (PCB3233 Exam 4) |
University of Central Florida
1. Which of the following is the primary immunoglobulin isotype involved in Type I
hypersensitivity reactions?
A. IgG
B. IgM
C. IgE
D. IgA
Correct Answer: C
Explanation: Type I hypersensitivity is mediated by IgE antibodies that bind to high-
affinity Fc receptors on mast cells and basophils. Upon subsequent exposure to an allergen,
these cells cross-link and degranulate, releasing histamine and other inflammatory
mediators. This rapid response characterizes immediate hypersensitivity symptoms like
anaphylaxis and asthma.
2. Delayed-type hypersensitivity (Type IV) is primarily mediated by which of the following
immune components?
A. T lymphocytes
B. Complement system
,C. Plasma cells
D. Immune complexes
Correct Answer: A
Explanation: Type IV hypersensitivity is a cell-mediated response rather than an antibody-
mediated one. It involves the activation of Th1 cells and CD8 T cells that release cytokines
to recruit and activate macrophages. This process takes 48 to 72 hours to manifest
clinically, as seen in the tuberculin skin test.
3. What is the primary immunological mechanism responsible for Myasthenia Gravis?
A. Immune complex deposition in the joints
B. Antibody-mediated blocking of acetylcholine receptors
C. T cell destruction of the myelin sheath
D. Mast cell degranulation in the neuromuscular junction
Correct Answer: B
Explanation: In Myasthenia Gravis, autoantibodies are produced against the nicotinic
acetylcholine receptors at the neuromuscular junction. These antibodies block the binding
of acetylcholine and trigger receptor internalisation and degradation. This leads to
impaired neuromuscular transmission and progressive muscle weakness.
, 4. A patient experiences a rapid rejection of a kidney transplant within minutes of the
procedure. This is likely due to:
A. Hyperacute rejection due to pre-existing ABO or HLA antibodies
B. Acute rejection mediated by T cells
C. Chronic rejection mediated by smooth muscle proliferation
D. Graft-versus-host disease initiated by donor lymphocytes
Correct Answer: A
Explanation: Hyperacute rejection occurs almost immediately after the graft is
vascularized. It is caused by pre-existing circulating antibodies in the recipient that
recognize antigens on the donor vascular endothelium. This triggers the complement
cascade and rapid thrombosis, leading to graft failure.
5. Systemic Lupus Erythematosus (SLE) is characterized by the presence of autoantibodies
against:
A. Thyroid peroxidase
B. Double-stranded DNA and nuclear proteins
C. The Fc portion of IgG
D. Red blood cell surface antigens
Correct Answer: B
Actual Q&A with Rationale (PCB3233 Exam 4) |
University of Central Florida
1. Which of the following is the primary immunoglobulin isotype involved in Type I
hypersensitivity reactions?
A. IgG
B. IgM
C. IgE
D. IgA
Correct Answer: C
Explanation: Type I hypersensitivity is mediated by IgE antibodies that bind to high-
affinity Fc receptors on mast cells and basophils. Upon subsequent exposure to an allergen,
these cells cross-link and degranulate, releasing histamine and other inflammatory
mediators. This rapid response characterizes immediate hypersensitivity symptoms like
anaphylaxis and asthma.
2. Delayed-type hypersensitivity (Type IV) is primarily mediated by which of the following
immune components?
A. T lymphocytes
B. Complement system
,C. Plasma cells
D. Immune complexes
Correct Answer: A
Explanation: Type IV hypersensitivity is a cell-mediated response rather than an antibody-
mediated one. It involves the activation of Th1 cells and CD8 T cells that release cytokines
to recruit and activate macrophages. This process takes 48 to 72 hours to manifest
clinically, as seen in the tuberculin skin test.
3. What is the primary immunological mechanism responsible for Myasthenia Gravis?
A. Immune complex deposition in the joints
B. Antibody-mediated blocking of acetylcholine receptors
C. T cell destruction of the myelin sheath
D. Mast cell degranulation in the neuromuscular junction
Correct Answer: B
Explanation: In Myasthenia Gravis, autoantibodies are produced against the nicotinic
acetylcholine receptors at the neuromuscular junction. These antibodies block the binding
of acetylcholine and trigger receptor internalisation and degradation. This leads to
impaired neuromuscular transmission and progressive muscle weakness.
, 4. A patient experiences a rapid rejection of a kidney transplant within minutes of the
procedure. This is likely due to:
A. Hyperacute rejection due to pre-existing ABO or HLA antibodies
B. Acute rejection mediated by T cells
C. Chronic rejection mediated by smooth muscle proliferation
D. Graft-versus-host disease initiated by donor lymphocytes
Correct Answer: A
Explanation: Hyperacute rejection occurs almost immediately after the graft is
vascularized. It is caused by pre-existing circulating antibodies in the recipient that
recognize antigens on the donor vascular endothelium. This triggers the complement
cascade and rapid thrombosis, leading to graft failure.
5. Systemic Lupus Erythematosus (SLE) is characterized by the presence of autoantibodies
against:
A. Thyroid peroxidase
B. Double-stranded DNA and nuclear proteins
C. The Fc portion of IgG
D. Red blood cell surface antigens
Correct Answer: B
