UTA Microbiology - Tholen Exam 4 | 60 Questions | 2026 Verified Answers with Rationales
UTA Microbiology Tholen Exam 4 2026
Actual Questions with Verified Answers, 100% Guarantee Pass
60 Multiple-Choice Questions | Immunology, Pathogenesis, Epidemiology, Antimicrobials, Diagnostics, Case Studies
Section 1: Immunology and Host-Pathogen Interactions (Q1-Q15)
Innate Immunity, Adaptive Immunity, Antigens, Antibodies, Cytokines, Hypersensitivity Reactions, and Immunodeficiency
Q1: A 28-year-old patient presents with recurrent bacterial infections. Laboratory analysis reveals normal T-cell counts but an
absence of B cells in peripheral blood. Genetic testing identifies a mutation in the BTK gene. Which of the following best
describes this condition?
A. Severe Combined Immunodeficiency (SCID)
B. X-linked agammaglobulinemia (Bruton's disease) [CORRECT]
C. DiGeorge syndrome
D. Acquired immunodeficiency syndrome (AIDS)
Correct Answer: B
Rationale: X-linked agammaglobulinemia is caused by a BTK gene mutation on the X chromosome, resulting in a block in B-cell maturation and
absent B cells and immunoglobulins. SCID involves both T and B cell defects, DiGeorge syndrome involves T-cell deficiency due to thymic
hypoplasia, and AIDS is an acquired secondary immunodeficiency caused by HIV destroying CD4+ T cells.
Q2: A researcher is studying pattern recognition receptors (PRRs) and their ligands. Which of the following is the correct
pairing of a Toll-like receptor (TLR) with its specific pathogen-associated molecular pattern (PAMP)?
A. TLR4 recognizes peptidoglycan from Gram-positive bacteria
B. TLR5 recognizes lipopolysaccharide (LPS) from Gram-negative bacteria
C. TLR4 recognizes lipopolysaccharide (LPS) from Gram-negative bacteria [CORRECT]
D. TLR3 recognizes flagellin from motile bacteria
Correct Answer: C
Rationale: TLR4 is the primary receptor for LPS, a major component of the outer membrane of Gram-negative bacteria. TLR5 recognizes flagellin,
not LPS. TLR2 (with TLR6 or TLR1) recognizes peptidoglycan and lipoteichoic acid from Gram-positive bacteria. TLR3 recognizes double-stranded
viral RNA, not flagellin.
Q3: A 35-year-old woman arrives at the emergency department experiencing difficulty breathing, urticaria, and hypotension
within minutes after being stung by a wasp. Which hypersensitivity reaction best describes this presentation?
A. Type II hypersensitivity reaction (cytotoxic)
B. Type III hypersensitivity reaction (immune complex)
C. Type IV hypersensitivity reaction (delayed-type)
D. Type I hypersensitivity reaction (immediate, IgE-mediated) [CORRECT]
Correct Answer: D
Rationale: Anaphylaxis is the classic example of a Type I hypersensitivity reaction, which is IgE-mediated and occurs within minutes of allergen
exposure. Upon re-exposure, the allergen cross-links IgE bound to mast cells and basophils, triggering degranulation and release of histamine and
other mediators. Type II involves IgG/IgM attacking cell surfaces, Type III involves immune complex deposition, and Type IV is T-cell-mediated and
delayed (24-72 hours).
Q4: Which antibody class is most closely associated with the pathogenesis of Type I hypersensitivity reactions and is found
bound to the surface of mast cells and basophils?
A. IgG
B. IgM
C. IgA
Page 1
, UTA Microbiology - Tholen Exam 4 | 60 Questions | 2026 Verified Answers with Rationales
D. IgE [CORRECT]
Correct Answer: D
Rationale: IgE is the antibody class responsible for Type I (immediate) hypersensitivity reactions. IgE binds with high affinity to Fc receptors on mast
cells and basophils. Upon allergen cross-linking of surface-bound IgE, these cells degranulate and release histamine, leukotrienes, and
prostaglandins. IgG mediates opsonization and complement activation, IgM is first in primary responses, and IgA is predominant at mucosal
surfaces.
Q5: A patient develops a hemolytic transfusion reaction after receiving an incompatible blood transfusion. Laboratory
analysis detects antibodies bound to the surface of donor red blood cells. Which hypersensitivity mechanism is involved?
A. Type I: IgE-mediated mast cell degranulation
B. Type II: IgG or IgM-mediated cytotoxic reaction [CORRECT]
C. Type III: Immune complex deposition in tissues
D. Type IV: T-cell-mediated delayed reaction
Correct Answer: B
Rationale: Hemolytic transfusion reactions are classic Type II (cytotoxic) hypersensitivity, in which pre-formed IgG or IgM antibodies bind to
antigens on donor RBCs, leading to complement activation, membrane attack complex formation, and cell lysis. Type I involves IgE and mast cells,
Type III involves soluble immune complexes, and Type IV involves sensitized T cells.
Q6: A patient who received horse antiserum for snakebite treatment develops fever, joint pain, and glomerulonephritis 10
days later. Serum analysis reveals circulating immune complexes. Which hypersensitivity reaction is responsible?
A. Type I hypersensitivity
B. Type II hypersensitivity
C. Type III hypersensitivity (serum sickness) [CORRECT]
D. Type IV hypersensitivity
Correct Answer: C
Rationale: Serum sickness is the prototypical Type III hypersensitivity reaction, caused by deposition of antigen-antibody (immune) complexes in
small blood vessels, joints, and renal glomeruli. These complexes activate complement, attracting neutrophils that release lysosomal enzymes, causing
tissue damage. The onset is typically 7-14 days after antigen exposure. Type I is immediate and IgE-mediated, Type II is cytotoxic, and Type IV is
T-cell-mediated and delayed.
Q7: A 45-year-old healthcare worker develops redness, itching, and vesicular lesions on her hands 48 hours after wearing new
latex gloves. A patch test confirms latex allergy. Which hypersensitivity mechanism accounts for this delayed reaction?
A. Type I: IgE-mediated immediate reaction
B. Type II: IgG/IgM cytotoxic reaction
C. Type III: Immune complex-mediated reaction
D. Type IV: T-cell-mediated delayed-type hypersensitivity [CORRECT]
Correct Answer: D
Rationale: Contact dermatitis is the classic Type IV (delayed-type) hypersensitivity, mediated by sensitized CD4+ Th1 cells and CD8+ cytotoxic T
cells rather than antibodies. The delayed onset (24-72 hours) is a hallmark. Sensitized T cells release cytokines such as IFN-gamma that recruit and
activate macrophages, causing tissue damage. The TB skin test also operates via this mechanism.
Q8: A 22-year-old medical student has a positive Mantoux (PPD) tuberculin skin test, with 15 mm of induration at 48 hours.
This reaction is mediated by which of the following immune mechanisms?
A. IgE-mediated mast cell degranulation
B. IgG-mediated complement activation and cytolysis
C. Sensitized T-cell release of cytokines and macrophage activation [CORRECT]
D. Immune complex deposition and complement fixation
Correct Answer: C
Rationale: The Mantoux tuberculin skin test is a classic Type IV (delayed-type) hypersensitivity. When PPD is injected intradermally, previously
sensitized T cells recognize the antigen, proliferate, and release cytokines (especially IFN-gamma) that activate macrophages, causing localized
induration peaking at 48-72 hours. It is not antibody-mediated.
Page 2
UTA Microbiology Tholen Exam 4 2026
Actual Questions with Verified Answers, 100% Guarantee Pass
60 Multiple-Choice Questions | Immunology, Pathogenesis, Epidemiology, Antimicrobials, Diagnostics, Case Studies
Section 1: Immunology and Host-Pathogen Interactions (Q1-Q15)
Innate Immunity, Adaptive Immunity, Antigens, Antibodies, Cytokines, Hypersensitivity Reactions, and Immunodeficiency
Q1: A 28-year-old patient presents with recurrent bacterial infections. Laboratory analysis reveals normal T-cell counts but an
absence of B cells in peripheral blood. Genetic testing identifies a mutation in the BTK gene. Which of the following best
describes this condition?
A. Severe Combined Immunodeficiency (SCID)
B. X-linked agammaglobulinemia (Bruton's disease) [CORRECT]
C. DiGeorge syndrome
D. Acquired immunodeficiency syndrome (AIDS)
Correct Answer: B
Rationale: X-linked agammaglobulinemia is caused by a BTK gene mutation on the X chromosome, resulting in a block in B-cell maturation and
absent B cells and immunoglobulins. SCID involves both T and B cell defects, DiGeorge syndrome involves T-cell deficiency due to thymic
hypoplasia, and AIDS is an acquired secondary immunodeficiency caused by HIV destroying CD4+ T cells.
Q2: A researcher is studying pattern recognition receptors (PRRs) and their ligands. Which of the following is the correct
pairing of a Toll-like receptor (TLR) with its specific pathogen-associated molecular pattern (PAMP)?
A. TLR4 recognizes peptidoglycan from Gram-positive bacteria
B. TLR5 recognizes lipopolysaccharide (LPS) from Gram-negative bacteria
C. TLR4 recognizes lipopolysaccharide (LPS) from Gram-negative bacteria [CORRECT]
D. TLR3 recognizes flagellin from motile bacteria
Correct Answer: C
Rationale: TLR4 is the primary receptor for LPS, a major component of the outer membrane of Gram-negative bacteria. TLR5 recognizes flagellin,
not LPS. TLR2 (with TLR6 or TLR1) recognizes peptidoglycan and lipoteichoic acid from Gram-positive bacteria. TLR3 recognizes double-stranded
viral RNA, not flagellin.
Q3: A 35-year-old woman arrives at the emergency department experiencing difficulty breathing, urticaria, and hypotension
within minutes after being stung by a wasp. Which hypersensitivity reaction best describes this presentation?
A. Type II hypersensitivity reaction (cytotoxic)
B. Type III hypersensitivity reaction (immune complex)
C. Type IV hypersensitivity reaction (delayed-type)
D. Type I hypersensitivity reaction (immediate, IgE-mediated) [CORRECT]
Correct Answer: D
Rationale: Anaphylaxis is the classic example of a Type I hypersensitivity reaction, which is IgE-mediated and occurs within minutes of allergen
exposure. Upon re-exposure, the allergen cross-links IgE bound to mast cells and basophils, triggering degranulation and release of histamine and
other mediators. Type II involves IgG/IgM attacking cell surfaces, Type III involves immune complex deposition, and Type IV is T-cell-mediated and
delayed (24-72 hours).
Q4: Which antibody class is most closely associated with the pathogenesis of Type I hypersensitivity reactions and is found
bound to the surface of mast cells and basophils?
A. IgG
B. IgM
C. IgA
Page 1
, UTA Microbiology - Tholen Exam 4 | 60 Questions | 2026 Verified Answers with Rationales
D. IgE [CORRECT]
Correct Answer: D
Rationale: IgE is the antibody class responsible for Type I (immediate) hypersensitivity reactions. IgE binds with high affinity to Fc receptors on mast
cells and basophils. Upon allergen cross-linking of surface-bound IgE, these cells degranulate and release histamine, leukotrienes, and
prostaglandins. IgG mediates opsonization and complement activation, IgM is first in primary responses, and IgA is predominant at mucosal
surfaces.
Q5: A patient develops a hemolytic transfusion reaction after receiving an incompatible blood transfusion. Laboratory
analysis detects antibodies bound to the surface of donor red blood cells. Which hypersensitivity mechanism is involved?
A. Type I: IgE-mediated mast cell degranulation
B. Type II: IgG or IgM-mediated cytotoxic reaction [CORRECT]
C. Type III: Immune complex deposition in tissues
D. Type IV: T-cell-mediated delayed reaction
Correct Answer: B
Rationale: Hemolytic transfusion reactions are classic Type II (cytotoxic) hypersensitivity, in which pre-formed IgG or IgM antibodies bind to
antigens on donor RBCs, leading to complement activation, membrane attack complex formation, and cell lysis. Type I involves IgE and mast cells,
Type III involves soluble immune complexes, and Type IV involves sensitized T cells.
Q6: A patient who received horse antiserum for snakebite treatment develops fever, joint pain, and glomerulonephritis 10
days later. Serum analysis reveals circulating immune complexes. Which hypersensitivity reaction is responsible?
A. Type I hypersensitivity
B. Type II hypersensitivity
C. Type III hypersensitivity (serum sickness) [CORRECT]
D. Type IV hypersensitivity
Correct Answer: C
Rationale: Serum sickness is the prototypical Type III hypersensitivity reaction, caused by deposition of antigen-antibody (immune) complexes in
small blood vessels, joints, and renal glomeruli. These complexes activate complement, attracting neutrophils that release lysosomal enzymes, causing
tissue damage. The onset is typically 7-14 days after antigen exposure. Type I is immediate and IgE-mediated, Type II is cytotoxic, and Type IV is
T-cell-mediated and delayed.
Q7: A 45-year-old healthcare worker develops redness, itching, and vesicular lesions on her hands 48 hours after wearing new
latex gloves. A patch test confirms latex allergy. Which hypersensitivity mechanism accounts for this delayed reaction?
A. Type I: IgE-mediated immediate reaction
B. Type II: IgG/IgM cytotoxic reaction
C. Type III: Immune complex-mediated reaction
D. Type IV: T-cell-mediated delayed-type hypersensitivity [CORRECT]
Correct Answer: D
Rationale: Contact dermatitis is the classic Type IV (delayed-type) hypersensitivity, mediated by sensitized CD4+ Th1 cells and CD8+ cytotoxic T
cells rather than antibodies. The delayed onset (24-72 hours) is a hallmark. Sensitized T cells release cytokines such as IFN-gamma that recruit and
activate macrophages, causing tissue damage. The TB skin test also operates via this mechanism.
Q8: A 22-year-old medical student has a positive Mantoux (PPD) tuberculin skin test, with 15 mm of induration at 48 hours.
This reaction is mediated by which of the following immune mechanisms?
A. IgE-mediated mast cell degranulation
B. IgG-mediated complement activation and cytolysis
C. Sensitized T-cell release of cytokines and macrophage activation [CORRECT]
D. Immune complex deposition and complement fixation
Correct Answer: C
Rationale: The Mantoux tuberculin skin test is a classic Type IV (delayed-type) hypersensitivity. When PPD is injected intradermally, previously
sensitized T cells recognize the antigen, proliferate, and release cytokines (especially IFN-gamma) that activate macrophages, causing localized
induration peaking at 48-72 hours. It is not antibody-mediated.
Page 2
