Download MB 441 Immune System Mastery: 2025 Updated Exam with Answers & Explanations and more Exams Life Sciences in PDF only on Docsity!
MB 441 Immune System Mastery – 2025
Updated Exam with Answers & Explanations
Description: This fully updated 2025 MB 441 Exam covers everything you need to master the immune system—now restructured with 110 high-quality questions, detailed explanations, and modern immunology concepts. Perfect for pre-med, biology, and life science majors preparing for midterms, finals, or professional exams. Crisp formatting, clinically relevant questions, and expert-level clarity— your shortcut to exam confidence starts here. Download now and level up your grade the smart way!
MB 441 Immune System Mastery: 2025 Updated Exam with
Answers & Explanations
- What are the two branches of the immune system? A. Humoral and cellular B. Adaptive and innate C. Complement and antibody D. Inflammatory and non-inflammatory Answer: B. Adaptive and innate Explanation: The immune system is divided into the innate (evolutionarily ancient and non- specific) and adaptive (specific and memory-forming) branches.
- What is a pathogen? Answer: Any organism that causes disease Explanation: A pathogen refers to any microorganism or agent, such as bacteria, viruses, or fungi, that can cause illness in a host.
- What is an antigen? Answer: Any molecule that can elicit an immune response Explanation: Antigens are substances, often proteins or polysaccharides, that the immune system recognizes and responds to.
- What is an epitope? Answer: The part of an antigen that is specifically recognized by antigen receptors Explanation: Epitopes are the specific sites on antigens to which antibodies or T-cell receptors bind.
- How does tissue differentiation begin during development? Answer: When the blastula invaginates to form the gastrula Explanation: Gastrulation is the process that establishes the primary germ layers necessary for tissue development.
- What is the only layer of a gastrula that is truly shielded from the external environment? Answer: Mesoderm Explanation: The mesoderm is enveloped by the ectoderm and endoderm and is least exposed to the environment.
Answer: B. Enhancing phagocytosis by tagging pathogens Explanation: Opsonization marks pathogens for ingestion by phagocytes using molecules like C3b or antibodies.
- Which three immune cells are considered professional phagocytes? Answer: Macrophages, dendritic cells, and neutrophils Explanation: These cells can engulf pathogens and present antigens (except neutrophils which don’t present antigens efficiently).
- What is the primary role of inflammation? Answer: To limit pathogen spread and recruit immune effectors to the infection site Explanation: Inflammation increases vascular permeability and signals immune cells to localize to the site of infection.
- What cytokines are released by activated macrophages to trigger inflammation? A. IL-2 and IL- 4 B. IL-6 and IL- 10 C. IL-1β, TNF-α, IL- 6 D. IFN-α and IFN-β Answer: C. IL-1β, TNF-α, IL- 6 Explanation: These cytokines increase permeability, fever, and immune cell recruitment during inflammation.
- What type of immune response do lymphocytes provide? Answer: Antigen-specific adaptive immunity against all pathogen types Explanation: Lymphocytes (T and B cells) recognize specific antigens and generate memory for future responses.
- What is the function of monocytes in immune defense? Answer: They replenish tissue macrophages and dendritic cells for antigen detection and repair Explanation: Monocytes differentiate into macrophages and DCs in tissues to maintain immune surveillance.
- Which immune cells specialize in defending against parasitic worms and allergens? A. Neutrophils B. B cells C. Eosinophils, basophils, and mast cells D. NK cells Answer: C. Eosinophils, basophils, and mast cells Explanation: These cells release granules that target large extracellular parasites and also mediate allergic reactions.
- Which immune cell is most effective against extracellular bacteria through rapid killing? Answer: Neutrophils Explanation: Neutrophils are the first responders and kill bacteria using ROS and antimicrobial enzymes.
- Which immune cell acts as a sentinel in tissues and initiates adaptive immunity? Answer: Dendritic cells Explanation: Dendritic cells capture antigens, migrate to lymph nodes, and activate naïve T cells.
- What happens when dendritic cells detect a pathogen? A. They release histamine B. They migrate to secondary lymphoid organs to present antigen C. They form granulomas D. They differentiate into B cells Answer: B. They migrate to secondary lymphoid organs to present antigen Explanation: Upon antigen recognition, dendritic cells leave tissues and activate adaptive responses in lymph nodes.
- Which cell type replaces dead macrophages and dendritic cells in tissue? Answer: Monocytes Explanation: Circulating monocytes enter tissue and differentiate to replenish local innate cells.
- What are considered secondary lymphoid organs? Answer: Lymph nodes, spleen, appendix, and tonsils Explanation: These are the locations where lymphocytes encounter antigens and activate.
- What happens if a lymphocyte does not recognize its specific antigen in a secondary lymphoid organ? Answer: It exits via lymphatic circulation and returns to the blood Explanation: Non-activated lymphocytes recirculate continuously in search of their antigen.
- What are the four basic steps in launching an adaptive immune response? A. T cell selection, neutrophil activation, epitope elimination, antigen presentation B. Inflammation, antigen capture, lymphocyte activation, memory formation C. Inflammation, macrophage activation, cytokine suppression, antibody digestion D. Phagocytosis, tolerance, mast cell degranulation, cytokine production Answer: B. Inflammation, antigen capture, lymphocyte activation, memory formation Explanation: Adaptive immunity is triggered by innate signals and results in specific effector and memory cells.
- How many distinct antigens can a single antibody bind? Answer: One Explanation: Each antibody is specific to a single epitope on an antigen due to its unique variable region.
- What is the most critical protein in the complement cascade? A. C B. C5a C. C D. CD Answer: C. C Explanation: C3 is central to all complement pathways; its activation enables opsonization, inflammation, and MAC formation.
- What happens to C3 during activation? Answer: It’s cleaved to C3a and C3b; C3b binds pathogen surfaces via its exposed thioester bond
Explanation: C3b covalently attaches to pathogens to opsonize them, while C3a promotes inflammation.
- What are the three main effects of complement fixation? Answer:
- Opsonization for phagocytosis
- Membrane Attack Complex (MAC)-mediated lysis
- Inflammation induction Explanation: Complement proteins target and eliminate pathogens through these coordinated actions.
- Which protein prevents MAC formation on human cells? A. CD B. C1q C. CD D. MHC I Answer: C. CD Explanation: CD59 blocks the recruitment of C9 to prevent the formation of lytic pores on host cells.
- What role do C3a and C5a play during complement activation? Answer: They act as anaphylatoxins that enhance inflammation and recruit immune cells Explanation: These fragments increase vascular permeability and attract phagocytes to infection sites.
- What are acute-phase proteins? A. Antibodies produced during chronic infection B. Liver proteins induced by IL-6 that activate complement pathways C. Enzymes released by neutrophils D. Surface receptors on dendritic cells Answer: B. Liver proteins induced by IL-6 that activate complement pathways Explanation: Examples include C-reactive protein and mannose-binding lectin, which enhance innate defense.
Explanation: Examples include bacterial LPS and viral RNA, which trigger innate immune activation.
- What are PRRs (Pattern Recognition Receptors)? Answer: Immune receptors that detect PAMPs and initiate innate immune responses Explanation: These include toll-like receptors (TLRs) and NOD-like receptors.
- What happens when a PRR binds its corresponding PAMP? A. The cell undergoes apoptosis B. The cell inhibits antigen presentation C. The pathogen is ignored D. The immune cell becomes activated and initiates phagocytosis Answer: D. The immune cell becomes activated and initiates phagocytosis Explanation: This leads to internalization of the pathogen and production of inflammatory cytokines.
- Which receptors are the primary PAMP detectors in innate immunity? Answer: Toll-like receptors (TLRs) Explanation: TLRs are a major family of PRRs that recognize a wide range of microbial components.
- What is the role of TLR3 in immune signaling? A. Detects bacterial flagellin B. Recognizes viral double-stranded RNA in endosomes C. Binds to LPS on bacteria D. Activates eosinophils Answer: B. Recognizes viral double-stranded RNA in endosomes Explanation: TLR3 helps initiate antiviral responses by detecting viral nucleic acids.
- What does the TLR4:TLR4 homodimer recognize? Answer: Lipopolysaccharide (LPS) from gram-negative bacteria Explanation: TLR4 activation leads to a strong inflammatory response to bacterial infection.
- Which TLR detects single-stranded RNA viruses? A. TLR B. TLR C. TLR
D. TLR
Answer: C. TLR Explanation: TLR7 is found in endosomes and is activated by viral ssRNA.
- What immune cells typically express TLR9, which detects unmethylated CpG DNA? Answer: Plasmacytoid dendritic cells, B cells, eosinophils, and basophils Explanation: These cells recognize bacterial and viral DNA motifs to stimulate innate and adaptive immunity.
- What is the correct order of molecular interactions during TLR4 activation by LPS? A. MyD88 binds LPS → CD14 activates TRAF6 → NFκB enters nucleus B. CD14 binds LPS → MD2 facilitates TLR4 dimerization → MyD88 recruits IRAK4 → TRAF6 activates IKK → NFκB enters nucleus C. LPS binds to TLR4 → C3b is deposited → NFκB activation D. LPS binds to IL-6 → TNF-α is released → TRAF6 phosphorylates CD Answer: B. CD14 binds LPS → MD2 facilitates TLR4 dimerization → MyD88 recruits IRAK4 → TRAF6 activates IKK → NFκB enters nucleus Explanation: This cascade leads to activation of NFκB, which initiates transcription of inflammatory genes.
- What is the role of NFκB in immune signaling? Answer: It is a transcription factor that induces cytokine gene expression Explanation: NFκB is crucial in initiating immune responses by activating genes for inflammation and survival.
- Which receptors allow macrophages to detect intracellular peptidoglycans and activate NFκB? A. TLR B. CD C. NOD-like receptors D. ICAM- 1 Answer: C. NOD-like receptors Explanation: These cytoplasmic receptors recognize bacterial cell wall components inside cells.
Explanation: GPCR binding initiates intracellular signaling that guides immune cell migration.
- What are the four key adhesion molecules involved in leukocyte extravasation? A. TLR4, CD8, CRP, CD B. ICAM-1, L-selectin, CD34, LFA- 1 C. MyD88, IKK, CD14, IRAK D. MHC I, MHC II, CD4, CD Answer: B. ICAM-1, L-selectin, CD34, LFA- 1 Explanation: These molecules mediate neutrophil rolling, arrest, and transmigration through vessel walls.
- What is rolling adhesion during extravasation? Answer: The weak, transient binding of neutrophils to endothelial selectins Explanation: This slows neutrophils in the bloodstream, preparing them for firm adhesion.
- What allows neutrophils to stop rolling and firmly adhere to the endothelium? Answer: High-affinity binding of LFA-1 to ICAM- 1 Explanation: This tight binding allows the neutrophil to halt and prepare for transmigration.
- What is the term for immune cells squeezing through blood vessel walls into tissues? A. Opsonization B. Phagocytosis C. Diapedesis D. Chemotaxis Answer: C. Diapedesis Explanation: Diapedesis allows immune cells to enter infected tissues from circulation.
- What receptors do neutrophils use to recognize and bind to pathogens? Answer: Pattern Recognition Receptors (PRRs) and Complement Receptors Explanation: These receptors detect PAMPs and opsonized targets for phagocytosis.
- What happens inside a neutrophil during phagocytosis? A. Pathogen is stored for antigen presentation B. Pathogen is coated with antibodies C. Phagosome acidifies and fuses with granules and lysosomes D. Complement proteins are secreted
Answer: C. Phagosome acidifies and fuses with granules and lysosomes Explanation: This fusion delivers toxic enzymes and ROS to kill the ingested microbe.
- What is the main effector cell of the innate immune system for bacterial infections? Answer: Neutrophils Explanation: Neutrophils dominate early responses and are highly effective bacterial killers.
- Which molecules do phagocytic cells use to destroy pathogens inside phagosomes? Answer: Reactive oxygen species (ROS) Explanation: ROS are toxic compounds that damage microbial membranes, DNA, and proteins.
- What sequence best describes the innate immune response to extracellular bacteria? Answer:
- Epithelial barrier activation
- Complement and defensin release
- PRR recognition by macrophages
- Cytokine secretion
- Inflammation and lymph node activation
- Neutrophil extravasation and pathogen clearance Explanation: These steps coordinate rapid microbial detection and removal.
- What happens when viral PAMPs are recognized by TLRs and cytosolic sensors? Answer: Type I interferons are produced and antiviral genes are activated Explanation: Interferons establish an antiviral state, enhance NK function, and limit viral replication.
- Which toll-like receptors are expressed by almost all nucleated human cells to detect viral infections? Answer: TLR3, TLR7, and TLR Explanation: These TLRs detect various forms of viral RNA and DNA inside endosomes.
- What are the two functional types of receptors found on Natural Killer (NK) cells? A. CD4 and CD B. Activating and inhibitory receptors C. Pattern recognition and antibody receptors
C. It determines whether NKs proliferate or DCs mature based on cell abundance D. It activates complement Answer: C. It determines whether NKs proliferate or DCs mature based on cell abundance Explanation: IL- 15 - driven feedback ensures appropriate immune response magnitude.
- What process generates diverse antigen receptors in B and T lymphocytes? Answer: V(D)J recombination Explanation: This genetic recombination assembles variable regions for TCRs and antibodies.
- What are the basic steps of an adaptive immune response? Answer:
- Pathogen crosses epithelium
- Local innate response triggers inflammation
- Dendritic cells carry antigen to lymph nodes
- Lymphocytes are activated and clonally expand
- Effector cells migrate to infection site Explanation: Adaptive immunity provides specificity and memory following antigen exposure.
- What cells are classified as professional antigen-presenting cells (APCs)? A. T cells and NK cells B. Neutrophils, eosinophils, and mast cells C. Macrophages, dendritic cells, and B cells D. Epithelial cells and fibroblasts Answer: C. Macrophages, dendritic cells, and B cells Explanation: These APCs display antigen on MHC molecules and provide costimulatory signals.
- What is the function of the Major Histocompatibility Complex (MHC)? Answer: It presents processed antigen peptides to T cells Explanation: MHC molecules enable T cell recognition of intracellular and extracellular threats.
- What types of molecules can immunoglobulins (antibodies) recognize? Answer: Proteins, carbohydrates, lipids, and nucleic acids Explanation: Antibodies can bind a wide variety of antigens without MHC presentation.
- Which of the following best describes MHC Class I molecules? A. Expressed only on immune cells; present bacterial antigens B. Expressed by APCs; present exogenous antigens to CD4 T cells C. Expressed by most nucleated cells; present cytoplasmic antigens to CD8 T cells D. Only found on red blood cells Answer: C. Expressed by most nucleated cells; present cytoplasmic antigens to CD8 T cells Explanation: MHC-I enables detection of intracellular infections such as viruses.
- What describes the pathway of antigen presentation by MHC Class I? Answer:
- Virus infects host cell
- Viral proteins are degraded in the cytoplasm
- Peptides are loaded onto MHC-I in the ER
- MHC-I presents peptide on the cell surface
- CD8+ cytotoxic T cells recognize and kill infected cells Explanation: This process allows detection and elimination of infected host cells.
- What describes the MHC Class II antigen presentation pathway? Answer:
- Antigen is phagocytosed
- Degraded in the endosome
- Peptides loaded onto MHC-II in vesicles
- What is class switch recombination? Answer: A mechanism by which B cells change antibody isotype without altering antigen specificity Explanation: B cells can switch from producing IgM to IgG, IgA, or IgE to perform specialized functions.
- How are self-reactive lymphocytes removed to prevent autoimmunity? A. Positive selection B. Somatic recombination C. Negative selection D. Antigen presentation Answer: C. Negative selection Explanation: Self-reactive T and B cells are eliminated during development in the thymus or bone marrow.
- What is an allergen? Answer: A normally harmless antigen that induces an exaggerated IgE-mediated immune response Explanation: Allergens can trigger mast cell degranulation and cause allergic symptoms.
- What is diapedesis in immunology? Answer: The process by which immune cells exit blood vessels and enter tissues during inflammation Explanation: Also known as transmigration, it allows leukocytes to reach infection sites.
- Under what condition can the classical complement pathway be activated without inflammation? A. Presence of neutrophils B. Direct MBL binding C. Antibody binding to C1q D. T cell activation Answer: C. Antibody binding to C1q Explanation: In secondary responses, IgG or IgM antibodies bind to pathogens and activate C1q.
- What are interferons (IFNs)? Answer: Cytokines released in response to viral infections that enhance antiviral defenses Explanation: Type I interferons (IFN-α and IFN-β) block viral replication and activate NK and CTL responses.
- What does C1 inhibitor (C1INH) do in the complement system? Answer: Inhibits the proteases C1r, C1s, and MASPs to regulate complement activation Explanation: C1INH prevents excessive or misdirected complement activity.
- Can NK cells bind directly to bacteria? A. Yes, using PRRs B. No, because they lack bacterial recognition receptors C. Yes, if the bacteria express CD D. No, but only in secondary lymphoid organs Answer: B. No, because they lack bacterial recognition receptors Explanation: NK cells primarily target infected or transformed host cells, not free-living bacteria.
- What is the difference between iC3b and C3b in complement activation? Answer: iC3b is an inactive opsonin that cannot form convertase; C3b can form convertases Explanation: iC3b still aids in phagocytosis but cannot continue the complement cascade.
- What triggers the formation of soluble C3 convertase in the alternative pathway? Answer: Spontaneous hydrolysis of C3 near microbial surfaces with favorable charge Explanation: This leads to deposition of C3b on pathogen surfaces and cascade activation.
- Which of the following best describes MHC restriction in T cell responses? A. T cells recognize only antigens on B cell surfaces B. T cells require antigen presentation via self-MHC molecules C. T cells can bind free-floating antigen like antibodies D. MHC only presents viral peptides Answer: B. T cells require antigen presentation via self-MHC molecules Explanation: T cells recognize antigen only when presented on MHC molecules of the host.
