MIMG C185A Immunology Final Examination
2026 Questions and Answers Revised
Update | 100% Correct - UCLA.
Question 1
What is the first line of defense against invading pathogens, and which components are
involved?
A) Adaptive immunity; T cells and B cells
B) Innate immunity; physical barriers, phagocytes, and antimicrobial proteins
C) Inflammation; cytokines and chemokines
D) Complement system; only membrane attack complex
Answer: B
Rationale: Innate immunity is the immediate, non-specific defense present from birth. It
includes physical/chemical barriers (skin, mucus, stomach acid), cellular components
(phagocytes like neutrophils and macrophages), and soluble factors (complement
proteins, interferons). The complement system (answer D) is part of innate immunity but
is not the only component; answer B is the most comprehensive and correct .
Question 2
A researcher is studying the immune response in mice infected with an extracellular
bacterial pathogen. Which cytokine profile would indicate a protective Th2-biased
response?
,A) High IFN-γ and TNF-β
B) High IL-4, IL-5, and IL-10
C) High IL-2 and IL-12
D) High IFN-γ and IL-2
Answer: B
Rationale: Extracellular bacteria are best cleared by antibody-mediated immunity, which
is promoted by Th2 cells. Th2 cells produce IL-4, IL-5, and IL-10. IL-4 drives B-cell class
switching to IgE, IL-5 activates eosinophils, and IL-10 helps dampen excessive
inflammation. In contrast, a Th1 response (high IFN-γ, TNF-β, IL-2) is associated with
intracellular pathogens where cell-mediated immunity is required .
Question 3
Which of the following are functions of the complement system? (Select all that apply)
A) Opsonization to enhance phagocytosis
B) Direct killing of pathogens via the Membrane Attack Complex (MAC)
C) Activation of B cells to produce antibodies
D) Induction of inflammatory responses via anaphylatoxins (C3a, C5a)
Answer: A, B, D
Rationale: The complement system has multiple functions: opsonization (C3b enhances
phagocytosis), direct lysis via the MAC, and inflammation through anaphylatoxins.
Activation of B cells to produce antibodies is not a direct complement function; it is a
function of adaptive immunity .
,Question 4
The complement system is activated via three pathways. Which pathway is activated by
antigen-antibody complexes?
A) Lectin pathway
B) Alternative pathway
C) Classical pathway
D) All three pathways equally
Answer: C
Rationale: The classical pathway is initiated when C1q binds to the Fc region of
antibodies (IgM or IgG) that are bound to antigens. The lectin pathway is activated by
carbohydrate recognition, and the alternative pathway is activated spontaneously on
pathogen surfaces .
Question 5
Which cell type is considered a professional phagocyte of the innate immune system?
A) T lymphocyte
B) Neutrophil
C) B lymphocyte
D) Dendritic cell
Answer: B
Rationale: Phagocytes are cellular components of innate immunity that identify, engulf,
and destroy pathogens via phagocytosis. Neutrophils are key in the initial clearance of
infection. Antibodies are produced by B cells (adaptive immunity), and immunological
memory is a feature of adaptive immunity .
, Question 6
What cellular process describes the formation of a phagosome that fuses with a
lysosome to form a phagolysosome?
A) Apoptosis
B) Phagocytosis
C) Necrosis
D) Autophagy
Answer: B
Rationale: Phagocytosis is the process in which pathogens are engulfed into a
phagosome, which then fuses with lysosomes to form a phagolysosome. This allows the
pathogen to be digested by lysosomal enzymes .
Question 7
Which receptors on macrophages and neutrophils bind to antibody-coated pathogens
to stimulate phagocytosis?
A) Complement receptors (CR)
B) Toll-like receptors (TLR)
C) Fc receptors (FcR)
D) Scavenger receptors
Answer: C
Rationale: Fc receptors bind the Fc portion of antibodies that are attached to
pathogens (opsonization), enhancing phagocytosis. Complement receptors bind
complement-opsonized pathogens, but the question specifies antibody-coated
2026 Questions and Answers Revised
Update | 100% Correct - UCLA.
Question 1
What is the first line of defense against invading pathogens, and which components are
involved?
A) Adaptive immunity; T cells and B cells
B) Innate immunity; physical barriers, phagocytes, and antimicrobial proteins
C) Inflammation; cytokines and chemokines
D) Complement system; only membrane attack complex
Answer: B
Rationale: Innate immunity is the immediate, non-specific defense present from birth. It
includes physical/chemical barriers (skin, mucus, stomach acid), cellular components
(phagocytes like neutrophils and macrophages), and soluble factors (complement
proteins, interferons). The complement system (answer D) is part of innate immunity but
is not the only component; answer B is the most comprehensive and correct .
Question 2
A researcher is studying the immune response in mice infected with an extracellular
bacterial pathogen. Which cytokine profile would indicate a protective Th2-biased
response?
,A) High IFN-γ and TNF-β
B) High IL-4, IL-5, and IL-10
C) High IL-2 and IL-12
D) High IFN-γ and IL-2
Answer: B
Rationale: Extracellular bacteria are best cleared by antibody-mediated immunity, which
is promoted by Th2 cells. Th2 cells produce IL-4, IL-5, and IL-10. IL-4 drives B-cell class
switching to IgE, IL-5 activates eosinophils, and IL-10 helps dampen excessive
inflammation. In contrast, a Th1 response (high IFN-γ, TNF-β, IL-2) is associated with
intracellular pathogens where cell-mediated immunity is required .
Question 3
Which of the following are functions of the complement system? (Select all that apply)
A) Opsonization to enhance phagocytosis
B) Direct killing of pathogens via the Membrane Attack Complex (MAC)
C) Activation of B cells to produce antibodies
D) Induction of inflammatory responses via anaphylatoxins (C3a, C5a)
Answer: A, B, D
Rationale: The complement system has multiple functions: opsonization (C3b enhances
phagocytosis), direct lysis via the MAC, and inflammation through anaphylatoxins.
Activation of B cells to produce antibodies is not a direct complement function; it is a
function of adaptive immunity .
,Question 4
The complement system is activated via three pathways. Which pathway is activated by
antigen-antibody complexes?
A) Lectin pathway
B) Alternative pathway
C) Classical pathway
D) All three pathways equally
Answer: C
Rationale: The classical pathway is initiated when C1q binds to the Fc region of
antibodies (IgM or IgG) that are bound to antigens. The lectin pathway is activated by
carbohydrate recognition, and the alternative pathway is activated spontaneously on
pathogen surfaces .
Question 5
Which cell type is considered a professional phagocyte of the innate immune system?
A) T lymphocyte
B) Neutrophil
C) B lymphocyte
D) Dendritic cell
Answer: B
Rationale: Phagocytes are cellular components of innate immunity that identify, engulf,
and destroy pathogens via phagocytosis. Neutrophils are key in the initial clearance of
infection. Antibodies are produced by B cells (adaptive immunity), and immunological
memory is a feature of adaptive immunity .
, Question 6
What cellular process describes the formation of a phagosome that fuses with a
lysosome to form a phagolysosome?
A) Apoptosis
B) Phagocytosis
C) Necrosis
D) Autophagy
Answer: B
Rationale: Phagocytosis is the process in which pathogens are engulfed into a
phagosome, which then fuses with lysosomes to form a phagolysosome. This allows the
pathogen to be digested by lysosomal enzymes .
Question 7
Which receptors on macrophages and neutrophils bind to antibody-coated pathogens
to stimulate phagocytosis?
A) Complement receptors (CR)
B) Toll-like receptors (TLR)
C) Fc receptors (FcR)
D) Scavenger receptors
Answer: C
Rationale: Fc receptors bind the Fc portion of antibodies that are attached to
pathogens (opsonization), enhancing phagocytosis. Complement receptors bind
complement-opsonized pathogens, but the question specifies antibody-coated
