UTA MICROBIOLOGY THOLEN EXAM 4 2026/2027 | Actual
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Section 1: Immunology (Host Defenses, Innate & Adaptive Immunity)
(Questions 1-20)
Q1: A 6-month-old infant presents with recurrent bacterial infections. Laboratory studies
reveal absent tonsils and extremely low B cell counts in peripheral blood. Genetic
testing confirms a mutation in the BTK gene. Which immune deficiency is MOST likely
diagnosed?
A. DiGeorge syndrome with thymic aplasia and T cell deficiency
B. Severe combined immunodeficiency (SCID) affecting both B and T cells
C. X-linked agammaglobulinemia with absent B cell maturation [CORRECT]
D. Common variable immunodeficiency with normal B cell numbers
Correct Answer: C
Rationale: Per standard immunology texts (Tortora, Madigan) and CDC
immunodeficiency guidelines, X-linked agammaglobulinemia (XLA) is caused by BTK
gene mutations blocking B cell maturation from pre-B to immature B cells, resulting in
absent B cells, no antibody production, and recurrent bacterial infections after maternal
antibodies wane. Distractor A describes T cell deficiency; B would affect T cells as well;
D has normal B cell numbers but impaired function.
Q2: A patient receives the influenza vaccine and develops protective immunity. Two
months later, they are exposed to a different influenza strain and experience milder
,symptoms than unvaccinated contacts. Which immunological mechanism BEST
explains this partial protection?
A. Primary immune response with IgM production over 7-10 days
B. Cross-reactive memory B and T cells from vaccine providing partial recognition
[CORRECT]
C. Passive immunity from residual vaccine antigens circulating in blood
D. Innate immunity alone without adaptive immune involvement
Correct Answer: B
Rationale: Per ASM immunology principles and viral immunology, influenza vaccines
generate memory B and T cells that can cross-react with related strains through
conserved epitopes (hemagglutinin stalk, internal proteins), providing partial protection
even when exact match fails. Distractor A describes initial response timing incorrectly;
C confuses active immunity with passive; D ignores the vaccine-induced adaptive
response.
Q3: A patient with rheumatoid arthritis is treated with a drug that inhibits TNF-α. Which
component of the immune system is being targeted?
A. Cytotoxic T cell killing of infected cells
B. Helper T cell cytokine involved in inflammation and macrophage activation
[CORRECT]
C. B cell antibody production in germinal centers
D. Regulatory T cell suppression of autoimmunity
Correct Answer: B
Rationale: Per immunology and clinical guidelines (CDC, ASM), TNF-α is a
pro-inflammatory cytokine produced primarily by activated macrophages and Th1 cells;
blocking it reduces inflammation in autoimmune diseases like RA. Distractor A
describes perforin/granzyme mechanisms; C describes antibody production not
targeted by TNF inhibitors; D is opposite of TNF-α function.
,Q4: A patient presents with severe anaphylaxis after eating peanuts, developing
urticaria, bronchospasm, and hypotension within minutes. Which immunological
mechanism is responsible?
A. Type II cytotoxic reaction with IgG against cell surface antigens
B. Type III immune complex deposition in tissues causing inflammation
C. Type I immediate hypersensitivity with IgE-mediated mast cell degranulation
[CORRECT]
D. Type IV delayed hypersensitivity with T cell infiltration at 48-72 hours
Correct Answer: C
Rationale: Per hypersensitivity classification in standard microbiology texts (Tortora,
Murray), Type I immediate hypersensitivity involves IgE binding to Fcε receptors on
mast cells/basophils, cross-linking by allergen, and rapid degranulation releasing
histamine, leukotrienes, causing anaphylaxis within minutes. Distractor A describes
cytotoxic reactions (hemolytic anemia); B describes immune complex diseases (serum
sickness); D describes contact dermatitis/TB skin tests.
Q5: A macrophage encounters a bacterial pathogen and engulfs it. Which pattern
recognition receptor (PRR) on the macrophage surface recognizes bacterial
lipopolysaccharide (LPS)?
A. NOD-like receptor (NLR) recognizing intracellular peptidoglycan fragments
B. Toll-like receptor 4 (TLR4) recognizing extracellular LPS [CORRECT]
C. RIG-I-like receptor (RLR) recognizing viral RNA
D. Toll-like receptor 3 (TLR3) recognizing double-stranded RNA
Correct Answer: B
Rationale: Per innate immunity principles in ASM guidelines and immunology texts,
TLR4 (with MD-2 and CD14) is the primary transmembrane PRR recognizing bacterial
LPS from gram-negative bacteria, triggering NF-κB activation and inflammatory cytokine
, production. Distractor A describes intracellular NLRs; C and D describe viral RNA
recognition, not bacterial LPS.
Q6: A patient with HIV infection has a CD4+ T cell count of 180 cells/μL (normal
500-1400). Which opportunistic infection is MOST likely to develop at this stage?
A. Mycobacterium tuberculosis reactivation due to impaired Th1 responses [CORRECT]
B. Streptococcus pyogenes pharyngitis due to B cell deficiency
C. Aspergillus fumigatus invasive infection due to neutropenia
D. Clostridioides difficile colitis due to IgA deficiency
Correct Answer: A
Rationale: Per CDC HIV/AIDS guidelines and immunology, CD4+ T cells <200 cells/μL
defines AIDS; Th1 cells are critical for macrophage activation and control of intracellular
pathogens like Mycobacterium tuberculosis, making TB reactivation common at this
stage. Distractor B is controlled by antibodies/neutrophils; C requires profound
neutropenia; D is associated with antibiotic use, not HIV specifically.
Q7: A newborn receives maternal IgG antibodies across the placenta. What type of
immunity does this represent?
A. Active natural immunity from exposure to pathogens in utero
B. Active artificial immunity from vaccination during pregnancy
C. Passive natural immunity from antibody transfer without immune response
[CORRECT]
D. Passive artificial immunity from administration of immune globulin
Correct Answer: C
Rationale: Per immunology classification in standard texts, maternal IgG crossing the
placenta provides passive natural immunity—immediate protection without the infant's
immune system generating the response. Distractor A suggests fetal active immunity; B
Questions with Verified Answers | 100% Guarantee Pass |
Pass Guaranteed - A+ Graded
Section 1: Immunology (Host Defenses, Innate & Adaptive Immunity)
(Questions 1-20)
Q1: A 6-month-old infant presents with recurrent bacterial infections. Laboratory studies
reveal absent tonsils and extremely low B cell counts in peripheral blood. Genetic
testing confirms a mutation in the BTK gene. Which immune deficiency is MOST likely
diagnosed?
A. DiGeorge syndrome with thymic aplasia and T cell deficiency
B. Severe combined immunodeficiency (SCID) affecting both B and T cells
C. X-linked agammaglobulinemia with absent B cell maturation [CORRECT]
D. Common variable immunodeficiency with normal B cell numbers
Correct Answer: C
Rationale: Per standard immunology texts (Tortora, Madigan) and CDC
immunodeficiency guidelines, X-linked agammaglobulinemia (XLA) is caused by BTK
gene mutations blocking B cell maturation from pre-B to immature B cells, resulting in
absent B cells, no antibody production, and recurrent bacterial infections after maternal
antibodies wane. Distractor A describes T cell deficiency; B would affect T cells as well;
D has normal B cell numbers but impaired function.
Q2: A patient receives the influenza vaccine and develops protective immunity. Two
months later, they are exposed to a different influenza strain and experience milder
,symptoms than unvaccinated contacts. Which immunological mechanism BEST
explains this partial protection?
A. Primary immune response with IgM production over 7-10 days
B. Cross-reactive memory B and T cells from vaccine providing partial recognition
[CORRECT]
C. Passive immunity from residual vaccine antigens circulating in blood
D. Innate immunity alone without adaptive immune involvement
Correct Answer: B
Rationale: Per ASM immunology principles and viral immunology, influenza vaccines
generate memory B and T cells that can cross-react with related strains through
conserved epitopes (hemagglutinin stalk, internal proteins), providing partial protection
even when exact match fails. Distractor A describes initial response timing incorrectly;
C confuses active immunity with passive; D ignores the vaccine-induced adaptive
response.
Q3: A patient with rheumatoid arthritis is treated with a drug that inhibits TNF-α. Which
component of the immune system is being targeted?
A. Cytotoxic T cell killing of infected cells
B. Helper T cell cytokine involved in inflammation and macrophage activation
[CORRECT]
C. B cell antibody production in germinal centers
D. Regulatory T cell suppression of autoimmunity
Correct Answer: B
Rationale: Per immunology and clinical guidelines (CDC, ASM), TNF-α is a
pro-inflammatory cytokine produced primarily by activated macrophages and Th1 cells;
blocking it reduces inflammation in autoimmune diseases like RA. Distractor A
describes perforin/granzyme mechanisms; C describes antibody production not
targeted by TNF inhibitors; D is opposite of TNF-α function.
,Q4: A patient presents with severe anaphylaxis after eating peanuts, developing
urticaria, bronchospasm, and hypotension within minutes. Which immunological
mechanism is responsible?
A. Type II cytotoxic reaction with IgG against cell surface antigens
B. Type III immune complex deposition in tissues causing inflammation
C. Type I immediate hypersensitivity with IgE-mediated mast cell degranulation
[CORRECT]
D. Type IV delayed hypersensitivity with T cell infiltration at 48-72 hours
Correct Answer: C
Rationale: Per hypersensitivity classification in standard microbiology texts (Tortora,
Murray), Type I immediate hypersensitivity involves IgE binding to Fcε receptors on
mast cells/basophils, cross-linking by allergen, and rapid degranulation releasing
histamine, leukotrienes, causing anaphylaxis within minutes. Distractor A describes
cytotoxic reactions (hemolytic anemia); B describes immune complex diseases (serum
sickness); D describes contact dermatitis/TB skin tests.
Q5: A macrophage encounters a bacterial pathogen and engulfs it. Which pattern
recognition receptor (PRR) on the macrophage surface recognizes bacterial
lipopolysaccharide (LPS)?
A. NOD-like receptor (NLR) recognizing intracellular peptidoglycan fragments
B. Toll-like receptor 4 (TLR4) recognizing extracellular LPS [CORRECT]
C. RIG-I-like receptor (RLR) recognizing viral RNA
D. Toll-like receptor 3 (TLR3) recognizing double-stranded RNA
Correct Answer: B
Rationale: Per innate immunity principles in ASM guidelines and immunology texts,
TLR4 (with MD-2 and CD14) is the primary transmembrane PRR recognizing bacterial
LPS from gram-negative bacteria, triggering NF-κB activation and inflammatory cytokine
, production. Distractor A describes intracellular NLRs; C and D describe viral RNA
recognition, not bacterial LPS.
Q6: A patient with HIV infection has a CD4+ T cell count of 180 cells/μL (normal
500-1400). Which opportunistic infection is MOST likely to develop at this stage?
A. Mycobacterium tuberculosis reactivation due to impaired Th1 responses [CORRECT]
B. Streptococcus pyogenes pharyngitis due to B cell deficiency
C. Aspergillus fumigatus invasive infection due to neutropenia
D. Clostridioides difficile colitis due to IgA deficiency
Correct Answer: A
Rationale: Per CDC HIV/AIDS guidelines and immunology, CD4+ T cells <200 cells/μL
defines AIDS; Th1 cells are critical for macrophage activation and control of intracellular
pathogens like Mycobacterium tuberculosis, making TB reactivation common at this
stage. Distractor B is controlled by antibodies/neutrophils; C requires profound
neutropenia; D is associated with antibiotic use, not HIV specifically.
Q7: A newborn receives maternal IgG antibodies across the placenta. What type of
immunity does this represent?
A. Active natural immunity from exposure to pathogens in utero
B. Active artificial immunity from vaccination during pregnancy
C. Passive natural immunity from antibody transfer without immune response
[CORRECT]
D. Passive artificial immunity from administration of immune globulin
Correct Answer: C
Rationale: Per immunology classification in standard texts, maternal IgG crossing the
placenta provides passive natural immunity—immediate protection without the infant's
immune system generating the response. Distractor A suggests fetal active immunity; B
