Immunology Complement Pathways Quiz
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Questions and Answers

What type of cells are layered on top of Ficoll Hypaque after centrifugation?

  • Erythrocytes
  • Mononuclear cells (correct)
  • Platelets
  • Granulocytes

    • What does forward scatter in flow cytometry primarily indicate?

  • Cell granularity
  • Cell distribution
  • Cell size (correct)
  • Cell viability

    • What happens to cells during magnetic bead separation once they bind to the beads?

  • They migrate towards the magnet (correct)
  • They change shape dramatically
  • They dissolve into the surrounding liquid
  • They become inactive

    • What is the main purpose of the serology-based HLA typing technique?

    <p>To determine specific HLA type of lymphocytes</p> Signup and view all the answers

    Where do T cells mature in the body?

    <p>Thymus</p> Signup and view all the answers

    Which component of a flow cytometer is responsible for processing optic signals?

    <p>Electronics</p> Signup and view all the answers

    What indicates the effectiveness of cytotoxic T cells in killing target cells during an assay?

    <p>Release of radioactive isotopes</p> Signup and view all the answers

    What process measures the uptake of bacteria by neutrophils?

    <p>Phagocytosis</p> Signup and view all the answers

    What is the primary trigger for the classical complement pathway activation?

    <p>Ab-Ag complex formation</p> Signup and view all the answers

    What is the role of properdin in the complement cascade?

    <p>Stabilizes the C3bBb complex</p> Signup and view all the answers

    Which component first binds to C5b in the formation of the membrane attack complex (MAC)?

    <p>C6</p> Signup and view all the answers

    How are the components of the classical pathway named?

    <p>By number of order of discovery</p> Signup and view all the answers

    What functions do complements perform in the immune response?

    <p>Opsonization, inflammation, and cell lysis</p> Signup and view all the answers

    Which pathway is activated by mannose-binding lectin (MBL)?

    <p>MC-Lectin pathway</p> Signup and view all the answers

    What describes the buffy coat layer after blood centrifugation?

    <p>White blood cells and platelets</p> Signup and view all the answers

    What triggers spontaneous activation in the alternative complement pathway?

    <p>Presence of high concentrations of C3</p> Signup and view all the answers

    What role do B cells play in the adaptive immune response after vaccination?

    <p>They differentiate into plasma cells to produce antibodies.</p> Signup and view all the answers

    Which of the following is a characteristic of live attenuated vaccines?

    <p>Mimic natural infections closely.</p> Signup and view all the answers

    What is the primary purpose of adjuvants in vaccines?

    <p>To enhance immunogenicity and inflammation.</p> Signup and view all the answers

    What happens during the formation of memory cells after vaccination?

    <p>T cells and B cells are activated and persist long-term.</p> Signup and view all the answers

    Which statement about antibodies in the immune response is accurate?

    <p>IgE and IgG antibodies are produced through a Th2 response.</p> Signup and view all the answers

    What is one of the key properties shared by most cytokines?

    <p>They are rapidly secreted.</p> Signup and view all the answers

    Which of the following cytokines is NOT a pro-inflammatory cytokine?

    <p>IL10</p> Signup and view all the answers

    Which cytokine is essential for the differentiation of CD4+ Th0 T cells into the Th1 T cell subset?

    <p>Interleukin-6</p> Signup and view all the answers

    Where are T cells first activated in the body?

    <p>Lymph node</p> Signup and view all the answers

    Which statement about antigen presenting cells (APCs) is true?

    <p>They require activation before they can activate T cells.</p> Signup and view all the answers

    Which sequence correctly describes how B cells receive help from T cells?

    <p>B cell activation, Ag presentation, Cytokine secretion.</p> Signup and view all the answers

    Major Histocompatibility (MHC) Class I molecules primarily present which type of antigens?

    <p>Intracellular antigens to CD8+ T cells.</p> Signup and view all the answers

    Which of the following is FALSE regarding the activation of B cells?

    <p>B cells can activate T cells in the absence of antigens.</p> Signup and view all the answers

    What is the primary immune response associated with Type I food allergies?

    <p>Localised smooth muscle contraction and vasodilation</p> Signup and view all the answers

    During which phase do tumors evade the immune system through mutations?

    <p>Tumor escape</p> Signup and view all the answers

    Which lymphocyte subset is primarily responsible for inducing apoptosis in target tumor cells?

    <p>Cytotoxic T cells</p> Signup and view all the answers

    What mechanism allows tumors to evade immune surveillance via checkpoint proteins?

    <p>Immune checkpoint activation</p> Signup and view all the answers

    Which is NOT one of the key concepts in tumor immunology?

    <p>Immune response always prevents tumor growth</p> Signup and view all the answers

    What is one reason for the generation of tumor antigens?

    <p>Mutations in oncogenes or tumor suppressor genes</p> Signup and view all the answers

    What immune cell functions primarily through cytokine release to attack tumor cells?

    <p>Natural killer cells</p> Signup and view all the answers

    Which process involves the immune system suppressing the growth of tumor cells while promoting malignancy?

    <p>Immune editing</p> Signup and view all the answers

    Study Notes

    Complement Pathways

    • Classical pathway: Activated by antibody-antigen complex. C1q binds to Fc regions of IgM or IgG. C1s becomes enzymatically active (C1s esterase), cleaves C4 into C4a and C4b. C4b binds to C2, which is cleaved into C2b and C2a to form C4b2a.
    • Lectin pathway: Activated by MBL binding to pathogen surfaces. MBL, MASP1 and 2 cleave C4 and C2 to form C3 convertase.
    • Alternative pathway: Continuously active at low levels of C3. Enhanced when C3b binds to foreign surfaces. C3bBb is the key component on the pathogen surface. Properdin stabilizes C3bBb for rapid response.
    • Convergence: All three pathways converge with the formation of C3 convertase.
    • Component Naming: Components of the classical pathway are named according to the order of their discovery.
    • Complement Functions:
      • Opsonization: Enhancing phagocytosis by macrophages and neutrophils
      • Inflammation: Triggering inflammation by attracting immune cells
      • Lysis: Directly lysing pathogens by forming the Membrane Attack Complex (MAC)
    • MAC Formation: C5b on the cell surface binds to C6, followed by C7 and C8. The resulting complex penetrates the cell membrane. C9 molecules then bind to form a pore, leading to cell lysis.
    • C1 Complex: Recognizes and binds pathogens. It is composed of C1q, C1r, and C1s.
      • C1q binds to antibody-antigen complexes or antigens.
      • Binding activates C1r, which in turn activates C1s.
      • C1s cleaves C4 and C2, forming C3 convertase.
    • C1s Action: When C1s binds to antibody-antigen complexes, it becomes enzymatically active (C1s esterase).
    • Opsonins: Molecules that enhance phagocytosis of particles by macrophages and neutrophils.

    Blood Cell Separation

    • Centrifugation Layers:
      • RBC layer: Red blood cells
      • Buffy Coat: White blood cells
      • Plasma layer: Plasma
    • Density Gradient Centrifugation: This technique improves separation of WBCs by:
      • Increasing the purity of WBCs
      • Enhancing recovery and yield of cells
      • Providing specificity for different WBC subtypes
    • Ficoll Hypaque Centrifugation:
      • Top layer: Mononuclear cells
      • Middle layer: Ficoll Hypaque
      • Bottom layer: RBCs and granulocytes
      • Above mononuclear cell layer: Platelets and plasma
    • Magnetic Bead Separation: Small magnetic beads coated with monoclonal antibodies are added to blood and incubated. Specific cell types bind to the beads, forming rosettes. A magnet placed near the tube attracts the cell rosettes.
    • Flow Cytometry:
      • Forward Scatter: Measures cell size
      • Side Scatter: Measures cell granularity
      • Components:
        • Fluidics: A system that delivers a single-file suspension of cells.
        • Optics: Generates and collects light for analysis.
        • Electronics: Processes the optical signals.
      • Cell Sorting: Cells labeled with fluorescently tagged antibodies are directed to specific surface markers. Cells are measured by a laser, become charged, and are separated by an electric field.

    HLA Typing

    • Serology-based HLA Typing:
      • Serum containing specific anti-HLA antibodies is placed in tray wells.
      • Lymphocytes are added to the serum.
      • Rabbit complement is added. Lymphocytes expressing the specific HLA type form antigen-antibody complexes and are killed.
      • Dead cells are stained with eosin dye or ethidium bromide for detection.

    Neutrophil Functional Assays

    • Phagocytosis: Measures the uptake of bacteria or latex particles by counting or labeling.
    • Intracellular Killing: Uses Staphylococcus aureus to test for bacterial viability.
    • Directional Migration: Measures neutrophil movement through filters or gradients.
    • Surface Marker Up-regulation: Monclonal antibodies are used to measure changes in surface marker expression.

    Cytotoxic T Cell Functional Assays

    • Assay Principle: Measures the ability of cytotoxic T cells to kill target cells. Target cells are labeled with a radioactive isotope.
    • Assay Procedure: Target cells are mixed with lymphocytes and incubated. The release of radioactive isotope into the surrounding media indicates the T cell killing activity.

    B and T Lymphocytes

    • T cells: Mature in the thymus and are primed by antigens in the spleen and mucosal and cutaneous lymphoid tissue.
    • B cells: Mature in the bone marrow and are primed by antigens in the spleen, lymph nodes, and mucosal lymphoid tissue.
    • Dendritic cells: Activate macrophages via Th1 cells.

    Cytokines

    • Key Properties:
      • Low molecular weight proteins
      • Made in active and inactive forms
      • Rapid secretion
      • Brief and self-limiting secretion
      • Active at low concentrations
    • Interferons: The first cytokines to be identified.
    • Cytokine Redundancy: Multiple cytokines can perform the same function.
    • Pro-inflammatory Cytokines: TNF, IL1, IL6.
    • Th1 Development: Requires Interferon-gamma (IFNg), IL-2.

    B and T Cell Activation

    • T Cell Activation Site: Lymph nodes
    • T Cell Activation: Directly activated by antigen presented in MHC molecules on antigen presenting cells.
    • B Cell Activation: Activated by antigen presented by antigen presenting cells.
    • Antigen Presenting Cell Activation: APCs must be activated before they can activate a T cell.
    • Two Signal Activation: Both T and B cells require two signals:
      • Signal 1: T cells - Antigen presented in MHC molecules binding to TCR; B cells - Epitope binding to BCR.
      • Signal 2: T cells - Activated APC expressing co-stimulatory molecules; B cells - Cytokines secreted by activated T cells.

    B Cell Help from T Cells:

    • Steps:
      • B cell antigen recognition
      • Antigen processing and presentation by B cells
      • Interaction of B cells with CD4+ T cells
      • Co-stimulatory signals from activated T cells
      • Cytokine secretion by activated T cells
      • B cell activation and antibody secretion

    MHC Class I

    • MHC Class I molecules present intracellular antigens to CD8+ T cells.

    Hypersensitivity Reactions

    • Type I: Allergic reactions. Mast cell mediators cause smooth muscle contraction and vasodilation.
    • Type II: Transfusion reactions due to incompatible blood types. Transfused RBC bind IgM in serum, activating complement and destroying the transfused cells.
    • Type III: Immune complex-mediated hypersensitivity. Large amounts of IgG to antigens form insoluble immune complexes, causing tissue damage.
    • Type IV: Delayed-type hypersensitivity. Allergen presented by Langerhans cells, expanding Th1 clones. Re-exposure leads to skin inflammation.

    Tumor Immunology

    • Key Concepts:

      • Tumours express antigens recognized as foreign by the host immune system.
      • Immune responses often fail to prevent tumour growth.
      • The immune system can be activated to kill tumour cells.

    • Three Phases of Tumor Growth and Immune System Interaction:

      • Immune Surveillance: Recognition and elimination of abnormal cells.
      • Immune Editing: The immune system targets and kills some tumor cells, leading to tumor cell mutation to evade the IS.
      • Tumor Escape: Additional mutations allow tumor cells to escape immune surveillance.

    • Cancer Immunoediting: The process where the immune system suppresses tumor cell growth, promoting their malignancy.

    • Lymphocytes Involved in Tumor Cell Killing:

      • Cytotoxic T cells: Kill tumor cells via perforin and granzyme.
      • Natural Killer cells: Kill tumor cells via perforin, granzyme, and cytokine release (TNF and IFNy).

    • Tumor Antigen Origins:

      • Mutations: Oncogenes or tumor suppressor genes.
      • Overexpression: Proteins overexpressed in tumors.
      • Viral Antigens: In cancers associated with viral infections.
      • Post-translational Modifications: Glycosylation can create neoantigens.

    • Cancer Evasion Mechanisms:

      • Checkpoint Activation: Checkpoint proteins inhibit T cell attack on tumor cells.
      • Immunosuppressive Factors: Directly inhibit immune cells (IL-10 and TGFb).
      • Antigen Loss or Modulation: Down-regulation or mutation of tumor antigens reduces visibility to immune cells.

    • Macrophages: Can either inhibit or promote tumor growth. Macrophages can enhance CD8+ T cell response.

    Schistosomiasis:

    • Adaptive Immune Response:
      • Th2 response produces IL-4 and IL-13, activating eosinophils, basophils, and mast cells.
      • IgE and IgG antibodies are produced (ADCC).

    Immunization

    • Evidence for Antibody-based Vaccine Function:

      • Neutralization of Pathogens: Antibodies can directly neutralize pathogens.
      • Passive Immunization: Transferring antibodies confers protection.
      • Memory B Cell Responses: Long-lasting antibody production after vaccination.

    • Process of Vaccine-induced Immunity:

      • Antigen Introduction: Introducing the antigen.
      • Innate Immune Activation: Activation of dendritic cells and APCs.
      • Antigen Presentation to T cells: Antigen presentation to T cells.
      • T cell and B cell Activation: Activation of CD4+ and CD8+ T cells, and differentiation of B cells into antibody-producing plasma cells.
      • Memory Cell Formation: Formation of memory cells for long-term protection.

    • Differences between Live/Attenuated and Non-live Vaccines:

      • Live/Attenuated vaccines:
        • Long-lasting immunity.
        • Fewer doses required.
        • Uses weakened pathogens.
        • Mimic natural infection.
      • Non-live vaccines:
        • Shorter duration of immunity.
        • More doses required.
        • Use killed or inactive pathogens.
        • Stimulate humoral immunity (antibody production).

    • Methods to Improve Vaccine Responses:

      • Adjuvants: Promote inflammation, enhance antigen presentation, and stimulate specific immune pathways.
      • Increased Spacing: 8-week spacing between doses can improve memory responses.
      • Antigen Valency/Affinity: Altering antigen properties can influence B cell receptor activity.

    • True or False:

      • mRNA vaccines enter the nucleus: False.
      • Antibodies produced by B cells prevent infection: True
      • Adjuvants enhance immunogenicity: True

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    Immunology Notes PDF

    Description

    Test your knowledge on the classical, lectin, and alternative complement pathways in immunology. This quiz covers the mechanisms of activation, functions, and convergence of these pathways. Ideal for students studying immunology or related health sciences.

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