BMSC540 Immunology Practice Questions and Answers Updated
2026 | Complete Immunology Study Guide with Verified Questions,
Detailed Rationales, Innate and Adaptive Immunity, Antigen-
Antibody Interactions, Hypersensitivity Reactions, Autoimmune
Diseases, Immunodeficiency Disorders, Vaccines, Cytokines, MHC
Function & Biomedical Science Exam Prep
Question 1: Which of the following cell types is primarily responsible for producing
antibodies in the adaptive immune response?
A. Cytotoxic T cells
B. Natural killer cells
C. Dendritic cells
D. B lymphocytes
CORRECT ANSWER: D. B lymphocytes
Rationale: B lymphocytes (B cells) are the primary antibody-producing cells in the
adaptive immune system. Upon activation by antigen and helper T cells, they
differentiate into plasma cells that secrete large quantities of antigen-specific
antibodies.
Question 2: What is the main function of MHC class I molecules?
A. Presenting extracellular antigens to CD4+ T cells
B. Presenting intracellular antigens to CD8+ T cells
C. Activating B cells directly
D. Binding to Toll-like receptors on macrophages
CORRECT ANSWER: B. Presenting intracellular antigens to CD8+ T cells
Rationale: MHC class I molecules present peptides derived from intracellular
pathogens (e.g., viruses) to CD8+ cytotoxic T lymphocytes, enabling the immune system
to detect and eliminate infected cells.
Question 3: Which immunoglobulin isotype is most abundant in human serum?
A. IgA
B. IgE
C. IgG
D. IgM
CORRECT ANSWER: C. IgG
Rationale: IgG constitutes approximately 75–80% of total serum immunoglobulins and
plays a central role in systemic immunity, including opsonization, complement
activation, and neutralization of pathogens.
Question 4: Which of the following best describes the role of the thymus in the
immune system?
,A. Site of B cell maturation
B. Primary site of antibody production
C. Site of T cell maturation and selection
D. Storage organ for memory lymphocytes
CORRECT ANSWER: C. Site of T cell maturation and selection
Rationale: The thymus is the primary lymphoid organ where T cell precursors mature
and undergo positive and negative selection to ensure self-tolerance and functional
competence.
Question 5: What is the primary mechanism by which cytotoxic T lymphocytes kill
virus-infected cells?
A. Phagocytosis
B. Release of perforin and granzymes
C. Secretion of interleukin-4
D. Opsonization with complement
CORRECT ANSWER: B. Release of perforin and granzymes
Rationale: Cytotoxic T lymphocytes (CTLs) induce apoptosis in target cells by releasing
perforin (which forms pores in the target membrane) and granzymes (serine proteases
that activate apoptotic pathways).
Question 6: Which complement pathway is initiated by antigen-antibody
complexes?
A. Alternative pathway
B. Lectin pathway
C. Classical pathway
D. Terminal pathway
CORRECT ANSWER: C. Classical pathway
Rationale: The classical complement pathway is activated when C1q binds to antigen-
antibody complexes, typically involving IgM or IgG, leading to a cascade that results in
pathogen lysis and inflammation.
Question 7: Which cytokine is primarily responsible for promoting the
differentiation of naïve CD4+ T cells into Th1 cells?
A. IL-4
B. IL-10
C. IL-12
D. TGF-β
CORRECT ANSWER: C. IL-12
, Rationale: IL-12, produced by antigen-presenting cells such as dendritic cells and
macrophages, drives the differentiation of naïve CD4+ T cells toward the Th1 lineage,
which supports cell-mediated immunity against intracellular pathogens.
Question 8: What is the primary function of regulatory T cells (Tregs)?
A. Killing tumor cells
B. Producing high-affinity antibodies
C. Suppressing immune responses to maintain tolerance
D. Phagocytosing bacteria
CORRECT ANSWER: C. Suppressing immune responses to maintain tolerance
Rationale: Regulatory T cells (Tregs), often characterized by expression of FoxP3,
suppress effector T cell responses and prevent autoimmune reactions by maintaining
peripheral tolerance.
Question 9: Which of the following is a key feature of innate immunity?
A. Memory response upon re-exposure
B. High specificity for individual antigens
C. Immediate but non-specific defense
D. Requires weeks to develop after first exposure
CORRECT ANSWER: C. Immediate but non-specific defense
Rationale: Innate immunity provides rapid, generic defense mechanisms (e.g.,
phagocytosis, inflammation, complement) without antigen specificity or immunological
memory.
Question 10: Which receptor on macrophages recognizes pathogen-associated
molecular patterns (PAMPs)?
A. T cell receptor (TCR)
B. B cell receptor (BCR)
C. Toll-like receptor (TLR)
D. Fc receptor
CORRECT ANSWER: C. Toll-like receptor (TLR)
Rationale: Toll-like receptors (TLRs) are pattern recognition receptors (PRRs) expressed
on innate immune cells like macrophages that recognize conserved microbial
structures known as PAMPs, initiating inflammatory responses.
Question 11: What is the main function of the Fc region of an antibody?
A. Antigen binding
B. Complement activation and binding to Fc receptors
C. Crossing the blood-brain barrier
D. Initiating V(D)J recombination
2026 | Complete Immunology Study Guide with Verified Questions,
Detailed Rationales, Innate and Adaptive Immunity, Antigen-
Antibody Interactions, Hypersensitivity Reactions, Autoimmune
Diseases, Immunodeficiency Disorders, Vaccines, Cytokines, MHC
Function & Biomedical Science Exam Prep
Question 1: Which of the following cell types is primarily responsible for producing
antibodies in the adaptive immune response?
A. Cytotoxic T cells
B. Natural killer cells
C. Dendritic cells
D. B lymphocytes
CORRECT ANSWER: D. B lymphocytes
Rationale: B lymphocytes (B cells) are the primary antibody-producing cells in the
adaptive immune system. Upon activation by antigen and helper T cells, they
differentiate into plasma cells that secrete large quantities of antigen-specific
antibodies.
Question 2: What is the main function of MHC class I molecules?
A. Presenting extracellular antigens to CD4+ T cells
B. Presenting intracellular antigens to CD8+ T cells
C. Activating B cells directly
D. Binding to Toll-like receptors on macrophages
CORRECT ANSWER: B. Presenting intracellular antigens to CD8+ T cells
Rationale: MHC class I molecules present peptides derived from intracellular
pathogens (e.g., viruses) to CD8+ cytotoxic T lymphocytes, enabling the immune system
to detect and eliminate infected cells.
Question 3: Which immunoglobulin isotype is most abundant in human serum?
A. IgA
B. IgE
C. IgG
D. IgM
CORRECT ANSWER: C. IgG
Rationale: IgG constitutes approximately 75–80% of total serum immunoglobulins and
plays a central role in systemic immunity, including opsonization, complement
activation, and neutralization of pathogens.
Question 4: Which of the following best describes the role of the thymus in the
immune system?
,A. Site of B cell maturation
B. Primary site of antibody production
C. Site of T cell maturation and selection
D. Storage organ for memory lymphocytes
CORRECT ANSWER: C. Site of T cell maturation and selection
Rationale: The thymus is the primary lymphoid organ where T cell precursors mature
and undergo positive and negative selection to ensure self-tolerance and functional
competence.
Question 5: What is the primary mechanism by which cytotoxic T lymphocytes kill
virus-infected cells?
A. Phagocytosis
B. Release of perforin and granzymes
C. Secretion of interleukin-4
D. Opsonization with complement
CORRECT ANSWER: B. Release of perforin and granzymes
Rationale: Cytotoxic T lymphocytes (CTLs) induce apoptosis in target cells by releasing
perforin (which forms pores in the target membrane) and granzymes (serine proteases
that activate apoptotic pathways).
Question 6: Which complement pathway is initiated by antigen-antibody
complexes?
A. Alternative pathway
B. Lectin pathway
C. Classical pathway
D. Terminal pathway
CORRECT ANSWER: C. Classical pathway
Rationale: The classical complement pathway is activated when C1q binds to antigen-
antibody complexes, typically involving IgM or IgG, leading to a cascade that results in
pathogen lysis and inflammation.
Question 7: Which cytokine is primarily responsible for promoting the
differentiation of naïve CD4+ T cells into Th1 cells?
A. IL-4
B. IL-10
C. IL-12
D. TGF-β
CORRECT ANSWER: C. IL-12
, Rationale: IL-12, produced by antigen-presenting cells such as dendritic cells and
macrophages, drives the differentiation of naïve CD4+ T cells toward the Th1 lineage,
which supports cell-mediated immunity against intracellular pathogens.
Question 8: What is the primary function of regulatory T cells (Tregs)?
A. Killing tumor cells
B. Producing high-affinity antibodies
C. Suppressing immune responses to maintain tolerance
D. Phagocytosing bacteria
CORRECT ANSWER: C. Suppressing immune responses to maintain tolerance
Rationale: Regulatory T cells (Tregs), often characterized by expression of FoxP3,
suppress effector T cell responses and prevent autoimmune reactions by maintaining
peripheral tolerance.
Question 9: Which of the following is a key feature of innate immunity?
A. Memory response upon re-exposure
B. High specificity for individual antigens
C. Immediate but non-specific defense
D. Requires weeks to develop after first exposure
CORRECT ANSWER: C. Immediate but non-specific defense
Rationale: Innate immunity provides rapid, generic defense mechanisms (e.g.,
phagocytosis, inflammation, complement) without antigen specificity or immunological
memory.
Question 10: Which receptor on macrophages recognizes pathogen-associated
molecular patterns (PAMPs)?
A. T cell receptor (TCR)
B. B cell receptor (BCR)
C. Toll-like receptor (TLR)
D. Fc receptor
CORRECT ANSWER: C. Toll-like receptor (TLR)
Rationale: Toll-like receptors (TLRs) are pattern recognition receptors (PRRs) expressed
on innate immune cells like macrophages that recognize conserved microbial
structures known as PAMPs, initiating inflammatory responses.
Question 11: What is the main function of the Fc region of an antibody?
A. Antigen binding
B. Complement activation and binding to Fc receptors
C. Crossing the blood-brain barrier
D. Initiating V(D)J recombination
