MIMG C185A Final Exam | Questions and Answers
| 2026 Revised Update | 100% Correct - UCLA.
SECTION 1: INNATE IMMUNITY & COMPLEMENT
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
Correct 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) .
Question 2: 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)
Correct Answer: A, B, D
Rationale: Complement functions include opsonization (C3b), direct lysis via the
MAC (C5b-C9), and inflammation via anaphylatoxins (C3a, C5a). Activation of B
cells is a function of adaptive immunity .
,Question 3: Which pathway of the complement system is activated by antigen-
antibody complexes?
A) Classical pathway
B) Lectin pathway
C) Alternative pathway
D) Terminal pathway
Correct Answer: A
Rationale: The classical pathway is initiated by the binding of C1q to the Fc region
of IgM or IgG antibodies that are bound to antigen. This is the pathway most
directly linked to adaptive immune responses .
Question 4: A researcher adds heat-killed E. coli to the serum of a non-immune
mouse. The researcher detects complement-dependent opsonization. Which
pathway is most likely responsible?
A) Classical pathway
B) Lectin pathway
C) Alternative pathway
D) All three pathways
Correct Answer: B
Rationale: E. coli expresses mannose on its cell surface. The lectin pathway is
activated when mannose-binding lectin (MBL) binds to these mannose residues in
the absence of specific antibodies, making it the most likely pathway in a non-
immune animal .
Question 5: What is the primary function of anaphylatoxins C3a and C5a?
A) Direct lysis of bacteria
B) Recruitment and activation of inflammatory cells
,C) Opsonization of pathogens
D) Activation of B cells
Correct Answer: B
Rationale: C3a and C5a are small complement fragments that act as
anaphylatoxins. They induce inflammation by causing mast cell degranulation,
increasing vascular permeability, and acting as potent chemoattractants for
neutrophils and other immune cells .
Question 6: What is the primary mechanism by which endotoxin (LPS) triggers
septic shock?
A) It directly lyses endothelial cells
B) It binds to Toll-like receptor 4 (TLR4) on immune cells, inducing massive
cytokine release
C) It blocks protein synthesis in hepatocytes
D) It degrades extracellular matrix collagen
Correct Answer: B
Rationale: Lipopolysaccharide (LPS), a component of Gram-negative outer
membranes, is recognized by the TLR4-MD-2 complex. This triggers NF-κB
activation and overproduction of TNF-α, IL-1, and IL-6, leading to systemic
inflammation, hypotension, and organ failure .
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
Correct Answer: C
, Rationale: Fc receptors bind the Fc portion of antibodies attached to pathogens, a
process called opsonization. This enhances phagocytosis. Complement receptors
bind complement-opsonized pathogens, but the question specifies antibody-
coated pathogens .
Question 8: A patient has a deficiency in C9. Which complement function will be
most severely affected?
A) Opsonization
B) Chemotaxis
C) Formation of the Membrane Attack Complex (MAC)
D) Activation of the alternative pathway
Correct Answer: C
Rationale: C9 is the final component of the MAC, polymerizing to form pores in the
target membrane. Deficiencies of C9 impair direct complement-mediated lysis. C3b
opsonization is still intact because C3 is upstream of C9 .
SECTION 2: ADAPTIVE IMMUNITY & ANTIGEN PRESENTATION
Question 9: Which of the following is a primary lymphoid organ responsible for
the maturation of T lymphocytes?
A) Spleen
B) Lymph node
C) Thymus
D) Bone marrow
Correct Answer: C
Rationale: The thymus is the primary lymphoid organ where T lymphocytes
mature. Bone marrow is the site of B cell maturation. Spleen and lymph nodes are
secondary lymphoid organs .
| 2026 Revised Update | 100% Correct - UCLA.
SECTION 1: INNATE IMMUNITY & COMPLEMENT
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
Correct 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) .
Question 2: 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)
Correct Answer: A, B, D
Rationale: Complement functions include opsonization (C3b), direct lysis via the
MAC (C5b-C9), and inflammation via anaphylatoxins (C3a, C5a). Activation of B
cells is a function of adaptive immunity .
,Question 3: Which pathway of the complement system is activated by antigen-
antibody complexes?
A) Classical pathway
B) Lectin pathway
C) Alternative pathway
D) Terminal pathway
Correct Answer: A
Rationale: The classical pathway is initiated by the binding of C1q to the Fc region
of IgM or IgG antibodies that are bound to antigen. This is the pathway most
directly linked to adaptive immune responses .
Question 4: A researcher adds heat-killed E. coli to the serum of a non-immune
mouse. The researcher detects complement-dependent opsonization. Which
pathway is most likely responsible?
A) Classical pathway
B) Lectin pathway
C) Alternative pathway
D) All three pathways
Correct Answer: B
Rationale: E. coli expresses mannose on its cell surface. The lectin pathway is
activated when mannose-binding lectin (MBL) binds to these mannose residues in
the absence of specific antibodies, making it the most likely pathway in a non-
immune animal .
Question 5: What is the primary function of anaphylatoxins C3a and C5a?
A) Direct lysis of bacteria
B) Recruitment and activation of inflammatory cells
,C) Opsonization of pathogens
D) Activation of B cells
Correct Answer: B
Rationale: C3a and C5a are small complement fragments that act as
anaphylatoxins. They induce inflammation by causing mast cell degranulation,
increasing vascular permeability, and acting as potent chemoattractants for
neutrophils and other immune cells .
Question 6: What is the primary mechanism by which endotoxin (LPS) triggers
septic shock?
A) It directly lyses endothelial cells
B) It binds to Toll-like receptor 4 (TLR4) on immune cells, inducing massive
cytokine release
C) It blocks protein synthesis in hepatocytes
D) It degrades extracellular matrix collagen
Correct Answer: B
Rationale: Lipopolysaccharide (LPS), a component of Gram-negative outer
membranes, is recognized by the TLR4-MD-2 complex. This triggers NF-κB
activation and overproduction of TNF-α, IL-1, and IL-6, leading to systemic
inflammation, hypotension, and organ failure .
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
Correct Answer: C
, Rationale: Fc receptors bind the Fc portion of antibodies attached to pathogens, a
process called opsonization. This enhances phagocytosis. Complement receptors
bind complement-opsonized pathogens, but the question specifies antibody-
coated pathogens .
Question 8: A patient has a deficiency in C9. Which complement function will be
most severely affected?
A) Opsonization
B) Chemotaxis
C) Formation of the Membrane Attack Complex (MAC)
D) Activation of the alternative pathway
Correct Answer: C
Rationale: C9 is the final component of the MAC, polymerizing to form pores in the
target membrane. Deficiencies of C9 impair direct complement-mediated lysis. C3b
opsonization is still intact because C3 is upstream of C9 .
SECTION 2: ADAPTIVE IMMUNITY & ANTIGEN PRESENTATION
Question 9: Which of the following is a primary lymphoid organ responsible for
the maturation of T lymphocytes?
A) Spleen
B) Lymph node
C) Thymus
D) Bone marrow
Correct Answer: C
Rationale: The thymus is the primary lymphoid organ where T lymphocytes
mature. Bone marrow is the site of B cell maturation. Spleen and lymph nodes are
secondary lymphoid organs .
