Kuby Immunology Exam 2026 – Practice Test Bank
250 Verified Questions with Detailed Rationales & Complete Study
Guide
Section 1: Innate Immunity (Questions 1–35)
1. Which of the following is considered the first line of defense in
the innate immune system? E) Memory cells
A) T lymphocytes
B) Antibodies produced by B cells
C) Physical barriers such as skin and mucous membranes
D) Complement proteins in the blood
Answer C: — Physical barriers such as skin and mucous membranes
Rationale: The first line of defense in innate immunity consists of
physical and chemical barriers, including the skin, mucous
,membranes, stomach acid, and antimicrobial peptides. These barriers
prevent pathogen entry before the immune system is engaged. T
lymphocytes and antibodies are part of adaptive immunity,
complement is a secondary innate response, and memory cells are
adaptive immune components. ---
2. Which pattern recognition receptor is primarily responsible for
detecting bacterial lipopolysaccharide (LPS)? E) TLR-11
A) TLR-1
B) TLR-4
C) TLR-7
D) TLR-9
Answer B: — TLR-4
Rationale: Toll-like receptor 4 (TLR-4) specifically recognizes and
binds to bacterial lipopolysaccharide (LPS), also known as endotoxin,
found on the outer membrane of gram-negative bacteria. This
recognition triggers a cascade of innate immune responses. Other
TLRs recognize different pathogen-associated molecular patterns:
TLR-1 and TLR-6 recognize lipoproteins, TLR-7 and TLR-8 recognize
RNA, and TLR-9 recognizes CpG DNA. ---
,3. What is the primary function of complement protein C3a? E)
Inhibiting viral replication
A) Direct lysis of bacterial cell membranes
B) Coating pathogens for opsonization
C) Acting as an anaphylatoxin to promote inflammation
D) Serving as the central recognition molecule
Answer C: — Acting as an anaphylatoxin to promote inflammation
Rationale: C3a is a small fragment generated during complement
activation that acts as a potent anaphylatoxin, inducing mast cell
degranulation and increased vascular permeability to promote local
inflammation. While C3b (the larger fragment from C3 cleavage)
serves as an opsonin, C3a's primary role is inflammatory. C5a is the
most potent anaphylatoxin. Direct lysis is primarily the role of the
membrane attack complex. ---
4. Which cells are primarily responsible for killing virus-infected cells
through antibody-dependent cellular cytotoxicity (ADCC)? E) Mast
cells
, A) Neutrophils only
B) Natural killer cells and macrophages
C) Eosinophils and basophils
D) Dendritic cells
Answer B: — Natural killer cells and macrophages
Rationale: Natural killer cells and macrophages are the primary
effector cells for ADCC. They recognize antibody-coated target cells
through their Fc receptors (CD16 on NK cells, CD64 on macrophages),
which crosslinks upon binding to the Fc region of antibodies,
triggering cytotoxic granule release. Neutrophils can participate but
are less efficient. Eosinophils, basophils, and mast cells are better
suited for parasitic defense, while dendritic cells primarily present
antigens. ---
5. Which of the following best describes the function of lysozyme in
innate immunity? E) Production of interferon-alpha
A) Opsonization of bacteria
B) Enzymatic degradation of bacterial peptidoglycan
C) Activation of the complement cascade
D) Recruitment of neutrophils
250 Verified Questions with Detailed Rationales & Complete Study
Guide
Section 1: Innate Immunity (Questions 1–35)
1. Which of the following is considered the first line of defense in
the innate immune system? E) Memory cells
A) T lymphocytes
B) Antibodies produced by B cells
C) Physical barriers such as skin and mucous membranes
D) Complement proteins in the blood
Answer C: — Physical barriers such as skin and mucous membranes
Rationale: The first line of defense in innate immunity consists of
physical and chemical barriers, including the skin, mucous
,membranes, stomach acid, and antimicrobial peptides. These barriers
prevent pathogen entry before the immune system is engaged. T
lymphocytes and antibodies are part of adaptive immunity,
complement is a secondary innate response, and memory cells are
adaptive immune components. ---
2. Which pattern recognition receptor is primarily responsible for
detecting bacterial lipopolysaccharide (LPS)? E) TLR-11
A) TLR-1
B) TLR-4
C) TLR-7
D) TLR-9
Answer B: — TLR-4
Rationale: Toll-like receptor 4 (TLR-4) specifically recognizes and
binds to bacterial lipopolysaccharide (LPS), also known as endotoxin,
found on the outer membrane of gram-negative bacteria. This
recognition triggers a cascade of innate immune responses. Other
TLRs recognize different pathogen-associated molecular patterns:
TLR-1 and TLR-6 recognize lipoproteins, TLR-7 and TLR-8 recognize
RNA, and TLR-9 recognizes CpG DNA. ---
,3. What is the primary function of complement protein C3a? E)
Inhibiting viral replication
A) Direct lysis of bacterial cell membranes
B) Coating pathogens for opsonization
C) Acting as an anaphylatoxin to promote inflammation
D) Serving as the central recognition molecule
Answer C: — Acting as an anaphylatoxin to promote inflammation
Rationale: C3a is a small fragment generated during complement
activation that acts as a potent anaphylatoxin, inducing mast cell
degranulation and increased vascular permeability to promote local
inflammation. While C3b (the larger fragment from C3 cleavage)
serves as an opsonin, C3a's primary role is inflammatory. C5a is the
most potent anaphylatoxin. Direct lysis is primarily the role of the
membrane attack complex. ---
4. Which cells are primarily responsible for killing virus-infected cells
through antibody-dependent cellular cytotoxicity (ADCC)? E) Mast
cells
, A) Neutrophils only
B) Natural killer cells and macrophages
C) Eosinophils and basophils
D) Dendritic cells
Answer B: — Natural killer cells and macrophages
Rationale: Natural killer cells and macrophages are the primary
effector cells for ADCC. They recognize antibody-coated target cells
through their Fc receptors (CD16 on NK cells, CD64 on macrophages),
which crosslinks upon binding to the Fc region of antibodies,
triggering cytotoxic granule release. Neutrophils can participate but
are less efficient. Eosinophils, basophils, and mast cells are better
suited for parasitic defense, while dendritic cells primarily present
antigens. ---
5. Which of the following best describes the function of lysozyme in
innate immunity? E) Production of interferon-alpha
A) Opsonization of bacteria
B) Enzymatic degradation of bacterial peptidoglycan
C) Activation of the complement cascade
D) Recruitment of neutrophils
