PCB 3233 Exam 4 V3 | 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. IgE
B. IgG
C. IgM
D. IgA
Answer: A
Rationale: Type I hypersensitivity reactions are mediated by the production of IgE
antibodies in response to specific allergens. These antibodies bind to high-affinity Fc
receptors on the surface of mast cells and basophils. Upon subsequent exposure, the
allergen cross-links the bound IgE, triggering the release of vasoactive amines like
histamine.
2. In Type II hypersensitivity, what is the primary mechanism of tissue damage?
A. Release of cytokines by sensitized T helper cells
B. Deposition of immune complexes in small blood vessels
,C. Antibody-mediated destruction of cells by complement or phagocytes
D. Degranulation of eosinophils following IgE cross-linking
Answer: C
Rationale: Type II hypersensitivity involves antibodies, usually IgG or IgM, directed
against antigens on the surface of host cells. This binding leads to cell death through
complement activation, opsonization, or antibody-dependent cellular cytotoxicity (ADCC).
Clinical examples include mismatched blood transfusions and hemolytic disease of the
newborn.
3. Which of the following conditions is a classic example of a Type III hypersensitivity
reaction?
A. Allergic rhinitis
B. Systemic Lupus Erythematosus (SLE)
C. Contact dermatitis
D. Goodpasture syndrome
Answer: B
Rationale: Type III hypersensitivity is characterized by the formation of soluble antigen-
antibody complexes that deposit in various tissues. In Systemic Lupus Erythematosus,
these complexes often settle in the kidneys, joints, and blood vessels, leading to systemic
inflammation. This process activates the complement cascade and recruits neutrophils that
cause extensive tissue damage.
, 4. Delayed-type hypersensitivity (DTH) is primarily mediated by which cell type?
A. B lymphocytes
B. Mast cells
C. Neutrophils
D. T lymphocytes
Answer: D
Rationale: Type IV hypersensitivity, or delayed-type hypersensitivity, is a cell-mediated
response rather than an antibody-mediated one. It involves sensitized Th1 or CD8+ T cells
that release cytokines to recruit and activate macrophages. The reaction typically takes 24
to 72 hours to develop after exposure to the antigen.
5. Hyperacute rejection of an organ transplant is caused by:
A. Activation of memory T cells within weeks of the procedure
B. Pre-existing antibodies against donor HLA or ABO antigens
C. Chronic fibrosis of the transplanted organ’s vasculature
D. Production of new antibodies months after the transplant
Answer: B
Rationale: Hyperacute rejection occurs within minutes to hours after the transplant is
vascularized. It is mediated by pre-existing antibodies in the recipient that recognize
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. IgE
B. IgG
C. IgM
D. IgA
Answer: A
Rationale: Type I hypersensitivity reactions are mediated by the production of IgE
antibodies in response to specific allergens. These antibodies bind to high-affinity Fc
receptors on the surface of mast cells and basophils. Upon subsequent exposure, the
allergen cross-links the bound IgE, triggering the release of vasoactive amines like
histamine.
2. In Type II hypersensitivity, what is the primary mechanism of tissue damage?
A. Release of cytokines by sensitized T helper cells
B. Deposition of immune complexes in small blood vessels
,C. Antibody-mediated destruction of cells by complement or phagocytes
D. Degranulation of eosinophils following IgE cross-linking
Answer: C
Rationale: Type II hypersensitivity involves antibodies, usually IgG or IgM, directed
against antigens on the surface of host cells. This binding leads to cell death through
complement activation, opsonization, or antibody-dependent cellular cytotoxicity (ADCC).
Clinical examples include mismatched blood transfusions and hemolytic disease of the
newborn.
3. Which of the following conditions is a classic example of a Type III hypersensitivity
reaction?
A. Allergic rhinitis
B. Systemic Lupus Erythematosus (SLE)
C. Contact dermatitis
D. Goodpasture syndrome
Answer: B
Rationale: Type III hypersensitivity is characterized by the formation of soluble antigen-
antibody complexes that deposit in various tissues. In Systemic Lupus Erythematosus,
these complexes often settle in the kidneys, joints, and blood vessels, leading to systemic
inflammation. This process activates the complement cascade and recruits neutrophils that
cause extensive tissue damage.
, 4. Delayed-type hypersensitivity (DTH) is primarily mediated by which cell type?
A. B lymphocytes
B. Mast cells
C. Neutrophils
D. T lymphocytes
Answer: D
Rationale: Type IV hypersensitivity, or delayed-type hypersensitivity, is a cell-mediated
response rather than an antibody-mediated one. It involves sensitized Th1 or CD8+ T cells
that release cytokines to recruit and activate macrophages. The reaction typically takes 24
to 72 hours to develop after exposure to the antigen.
5. Hyperacute rejection of an organ transplant is caused by:
A. Activation of memory T cells within weeks of the procedure
B. Pre-existing antibodies against donor HLA or ABO antigens
C. Chronic fibrosis of the transplanted organ’s vasculature
D. Production of new antibodies months after the transplant
Answer: B
Rationale: Hyperacute rejection occurs within minutes to hours after the transplant is
vascularized. It is mediated by pre-existing antibodies in the recipient that recognize
