BIOL 3201 – Immunology:
BIOL 3201 - IMMUNOLOGY EXAM QUESTIONS AND
CORRECT ANSWERS | LATEST 2026/2027
BIOL 3201 – IMMUNOLOGY
1. Which of the following best describes innate immunity?
A. It generates long-lived memory cells after first exposure
B. It relies on clonal expansion of antigen-specific lymphocytes
C. It provides rapid, non-specific defense that does not improve with
repeated exposure
D. It is mediated mainly by antibodies produced by plasma cells
ANSWER : C. It provides rapid, non-specific defense that does not
improve with repeated exposure
Innate defenses act within minutes to hours using germline-encoded
receptors and show no classic memory.
2. Pattern recognition receptors (PRRs) recognize which of the
following?
A. Self-antigens expressed by the thymus
B. Unique peptide epitopes presented on MHC class II
C. Rearranged immunoglobulin variable regions
D. Conserved microbial structures known as PAMPs
ANSWER : D. Conserved microbial structures known as PAMPs
PRRs detect conserved pathogen-associated molecular patterns such as LPS,
flagellin and viral nucleic acids.
Page 1 of 57
, BIOL 3201 – Immunology:
3. Toll-like receptor 4 (TLR4) is primarily activated by:
A. Bacterial flagellin
B. Unmethylated CpG DNA
C. Lipopolysaccharide from Gram-negative bacteria
D. Double-stranded viral RNA
ANSWER : C. Lipopolysaccharide from Gram-negative bacteria
TLR4, working with MD-2 and CD14, senses LPS from the outer membrane
of Gram-negative bacteria.
4. Which TLR recognizes bacterial flagellin?
A. TLR9
B. TLR7
C. TLR5
D. TLR3
ANSWER : C. TLR5
TLR5 binds the flagellin protein that makes up bacterial flagella.
5. TLR3, TLR7, TLR8 and TLR9 share which feature?
A. They detect bacterial cell wall lipoproteins at the cell surface
B. They signal exclusively through the TRIF-independent pathway
C. They are located in endosomal membranes and detect nucleic acids
D. They are expressed only on T lymphocytes
ANSWER : C. They are located in endosomal membranes and detect
nucleic acids
These TLRs sit in endosomes, where they sense viral and bacterial RNA or
DNA released after uptake.
6. The cytosolic sensor RIG-I primarily detects:
A. Fungal β-glucans
B. Bacterial peptidoglycan fragments
C. Extracellular ATP
D. Viral RNA bearing a 5′-triphosphate
ANSWER : D. Viral RNA bearing a 5′-triphosphate
RIG-I is a RIG-I-like receptor that recognizes short double-stranded viral
RNA with an uncapped 5′-triphosphate.
Page 2 of 57
, BIOL 3201 – Immunology:
7. NOD2 recognizes which bacterial component?
A. Muramyl dipeptide derived from peptidoglycan
B. Lipopolysaccharide
C. Lipoteichoic acid
D. Flagellin
ANSWER : A. Muramyl dipeptide derived from peptidoglycan
NOD2 is a cytosolic NOD-like receptor that senses muramyl dipeptide; NOD2
mutations are linked with Crohn disease.
8. Activation of the NLRP3 inflammasome leads directly to:
A. Release of perforin from cytotoxic T cells
B. Transport of peptides into the endoplasmic reticulum by TAP
C. Caspase-1 activation and processing of pro-IL-1β and pro-IL-18
D. Class switching in germinal center B cells
ANSWER : C. Caspase-1 activation and processing of pro-IL-1β and pro-
IL-18
The inflammasome assembles to activate caspase-1, which cleaves IL-1β and
IL-18 into their active forms and can trigger pyroptosis.
9. Which cell is the most abundant leukocyte in human blood and the
first to arrive at sites of acute bacterial infection?
A. Eosinophil
B. Basophil
C. Monocyte
D. Neutrophil
ANSWER : D. Neutrophil
Neutrophils make up roughly 50–70% of circulating leukocytes and
dominate early acute inflammation.
Page 3 of 57
, BIOL 3201 – Immunology:
10. The respiratory burst in phagocytes is generated by which enzyme
complex?
A. NADPH oxidase
B. Myeloperoxidase alone
C. Lysozyme
D. Adenylate cyclase
ANSWER : A. NADPH oxidase
NADPH oxidase reduces oxygen to superoxide, which is converted to other
reactive oxygen species used to kill microbes.
11. Chronic granulomatous disease results from a defect in:
A. Adenosine deaminase
B. CD40 ligand
C. NADPH oxidase
D. The common gamma chain
ANSWER : C. NADPH oxidase
Without functional NADPH oxidase, phagocytes cannot produce superoxide,
leaving patients prone to catalase-positive organisms.
12. Leukocyte adhesion deficiency type 1 is caused by a defect in:
A. MHC class I
B. Complement C3
C. CD18 (β2 integrin)
D. Sialyl-Lewis X
ANSWER : C. CD18 (β2 integrin)
Lack of CD18 prevents firm integrin-mediated adhesion, so neutrophils
cannot leave the blood; delayed umbilical cord separation is a classic sign.
13. During leukocyte extravasation, the initial rolling of neutrophils
along the endothelium is mediated mainly by:
A. Selectins binding sialylated carbohydrate ligands
B. Fc receptors binding IgG
C. CD28 binding B7
D. LFA-1 binding ICAM-1
ANSWER : A. Selectins binding sialylated carbohydrate ligands
Selectin-carbohydrate interactions are low affinity and produce rolling,
which precedes integrin-dependent firm adhesion.
Page 4 of 57
BIOL 3201 - IMMUNOLOGY EXAM QUESTIONS AND
CORRECT ANSWERS | LATEST 2026/2027
BIOL 3201 – IMMUNOLOGY
1. Which of the following best describes innate immunity?
A. It generates long-lived memory cells after first exposure
B. It relies on clonal expansion of antigen-specific lymphocytes
C. It provides rapid, non-specific defense that does not improve with
repeated exposure
D. It is mediated mainly by antibodies produced by plasma cells
ANSWER : C. It provides rapid, non-specific defense that does not
improve with repeated exposure
Innate defenses act within minutes to hours using germline-encoded
receptors and show no classic memory.
2. Pattern recognition receptors (PRRs) recognize which of the
following?
A. Self-antigens expressed by the thymus
B. Unique peptide epitopes presented on MHC class II
C. Rearranged immunoglobulin variable regions
D. Conserved microbial structures known as PAMPs
ANSWER : D. Conserved microbial structures known as PAMPs
PRRs detect conserved pathogen-associated molecular patterns such as LPS,
flagellin and viral nucleic acids.
Page 1 of 57
, BIOL 3201 – Immunology:
3. Toll-like receptor 4 (TLR4) is primarily activated by:
A. Bacterial flagellin
B. Unmethylated CpG DNA
C. Lipopolysaccharide from Gram-negative bacteria
D. Double-stranded viral RNA
ANSWER : C. Lipopolysaccharide from Gram-negative bacteria
TLR4, working with MD-2 and CD14, senses LPS from the outer membrane
of Gram-negative bacteria.
4. Which TLR recognizes bacterial flagellin?
A. TLR9
B. TLR7
C. TLR5
D. TLR3
ANSWER : C. TLR5
TLR5 binds the flagellin protein that makes up bacterial flagella.
5. TLR3, TLR7, TLR8 and TLR9 share which feature?
A. They detect bacterial cell wall lipoproteins at the cell surface
B. They signal exclusively through the TRIF-independent pathway
C. They are located in endosomal membranes and detect nucleic acids
D. They are expressed only on T lymphocytes
ANSWER : C. They are located in endosomal membranes and detect
nucleic acids
These TLRs sit in endosomes, where they sense viral and bacterial RNA or
DNA released after uptake.
6. The cytosolic sensor RIG-I primarily detects:
A. Fungal β-glucans
B. Bacterial peptidoglycan fragments
C. Extracellular ATP
D. Viral RNA bearing a 5′-triphosphate
ANSWER : D. Viral RNA bearing a 5′-triphosphate
RIG-I is a RIG-I-like receptor that recognizes short double-stranded viral
RNA with an uncapped 5′-triphosphate.
Page 2 of 57
, BIOL 3201 – Immunology:
7. NOD2 recognizes which bacterial component?
A. Muramyl dipeptide derived from peptidoglycan
B. Lipopolysaccharide
C. Lipoteichoic acid
D. Flagellin
ANSWER : A. Muramyl dipeptide derived from peptidoglycan
NOD2 is a cytosolic NOD-like receptor that senses muramyl dipeptide; NOD2
mutations are linked with Crohn disease.
8. Activation of the NLRP3 inflammasome leads directly to:
A. Release of perforin from cytotoxic T cells
B. Transport of peptides into the endoplasmic reticulum by TAP
C. Caspase-1 activation and processing of pro-IL-1β and pro-IL-18
D. Class switching in germinal center B cells
ANSWER : C. Caspase-1 activation and processing of pro-IL-1β and pro-
IL-18
The inflammasome assembles to activate caspase-1, which cleaves IL-1β and
IL-18 into their active forms and can trigger pyroptosis.
9. Which cell is the most abundant leukocyte in human blood and the
first to arrive at sites of acute bacterial infection?
A. Eosinophil
B. Basophil
C. Monocyte
D. Neutrophil
ANSWER : D. Neutrophil
Neutrophils make up roughly 50–70% of circulating leukocytes and
dominate early acute inflammation.
Page 3 of 57
, BIOL 3201 – Immunology:
10. The respiratory burst in phagocytes is generated by which enzyme
complex?
A. NADPH oxidase
B. Myeloperoxidase alone
C. Lysozyme
D. Adenylate cyclase
ANSWER : A. NADPH oxidase
NADPH oxidase reduces oxygen to superoxide, which is converted to other
reactive oxygen species used to kill microbes.
11. Chronic granulomatous disease results from a defect in:
A. Adenosine deaminase
B. CD40 ligand
C. NADPH oxidase
D. The common gamma chain
ANSWER : C. NADPH oxidase
Without functional NADPH oxidase, phagocytes cannot produce superoxide,
leaving patients prone to catalase-positive organisms.
12. Leukocyte adhesion deficiency type 1 is caused by a defect in:
A. MHC class I
B. Complement C3
C. CD18 (β2 integrin)
D. Sialyl-Lewis X
ANSWER : C. CD18 (β2 integrin)
Lack of CD18 prevents firm integrin-mediated adhesion, so neutrophils
cannot leave the blood; delayed umbilical cord separation is a classic sign.
13. During leukocyte extravasation, the initial rolling of neutrophils
along the endothelium is mediated mainly by:
A. Selectins binding sialylated carbohydrate ligands
B. Fc receptors binding IgG
C. CD28 binding B7
D. LFA-1 binding ICAM-1
ANSWER : A. Selectins binding sialylated carbohydrate ligands
Selectin-carbohydrate interactions are low affinity and produce rolling,
which precedes integrin-dependent firm adhesion.
Page 4 of 57
