The Immune Response - Part 2
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What is one of the primary functions of antibodies in the adaptive immune response?

  • Bind and neutralize bacterial toxins and viruses (correct)
  • Inhibit the activity of T-cells
  • Increase the production of red blood cells
  • Enhance the formation of new B-cells

    • How do antibodies promote the process of phagocytosis?

  • By increasing the size of the pathogen
  • By directly attacking the pathogen's cell wall
  • By forming a protective barrier around the host cell
  • By coating the pathogen through opsonization (correct)

    • Which types of antibodies activate the complement system?

  • IgD and IgM
  • IgA and IgE
  • IgG and IgM (correct)
  • IgE and IgA

    • What is the ultimate goal of the adaptive immune response as indicated in the content?

    <p>To target pathogens and their products for elimination</p> Signup and view all the answers

    Are antibodies specific or non-specific for their targets?

    <p>Specific for their targets</p> Signup and view all the answers

    What is the primary function of the Fab fragment in antibodies?

    <p>To bind to specific antigens</p> Signup and view all the answers

    Which regions are known as hypervariable regions in an antibody?

    <p>Complementary-determining regions (CDRs)</p> Signup and view all the answers

    What is the role of the Fc fragment in antibodies?

    <p>Binding to Fc receptors on immune cells</p> Signup and view all the answers

    During somatic recombination, which segments are joined to create the variable region of a light chain?

    <p>One V segment and one J segment</p> Signup and view all the answers

    Which statement is true regarding epitopes and antibodies?

    <p>B cells can recognize multiple epitopes of an antigen during an infection.</p> Signup and view all the answers

    What is the mass of a typical heavy chain in an antibody?

    <p>Approximately 50 kD or more</p> Signup and view all the answers

    What is the main purpose of junctional diversity in B cell antigen recognition?

    <p>To introduce additional variability in antibody structure</p> Signup and view all the answers

    What occurs when a B cell recognizes its specific antigen?

    <p>It multiplies and produces clones.</p> Signup and view all the answers

    Which part of an antibody is involved in forming disulfide bonds?

    <p>Fc fragment</p> Signup and view all the answers

    Why do B cells predominantly recognize external epitopes?

    <p>B cells are primarily involved in detecting surface infections.</p> Signup and view all the answers

    What is the main purpose of junctional diversity in B cell development?

    <p>To add new and random nucleotides to gene segments</p> Signup and view all the answers

    During B cell development, what is generated first?

    <p>Heavy chain</p> Signup and view all the answers

    What class of antibody is first secreted during an infection?

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

    What is the role of helper T cells in B cell activation?

    <p>To regulate the activities of other immune cells</p> Signup and view all the answers

    What role do MHC molecules play in the immune response?

    <p>They help to regulate tissue transplantation.</p> Signup and view all the answers

    What initiates class switching in B cells?

    <p>T cell help</p> Signup and view all the answers

    What are the different isotypes of MHC molecules expressed in humans?

    <p>Six MHC class I isotypes and five MHC class II isotypes.</p> Signup and view all the answers

    What is the term used for the specific version of a protein encoded by an allele?

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

    Which of the following best describes Class I MHC molecules?

    <p>They present infected cell peptides to CD8+ T cells</p> Signup and view all the answers

    What is the first step of B cell antigen recognition diversity?

    <p>Combinatorial diversity</p> Signup and view all the answers

    How do MHC class I and class II proteins differ at a structural level?

    <p>Class I proteins consist of only alpha chains while class II includes beta chains.</p> Signup and view all the answers

    What happens to B cells that do not encounter an antigen?

    <p>They undergo apoptosis</p> Signup and view all the answers

    What inheritance pattern do MHC alleles typically follow?

    <p>Individuals inherit one allele from each parent, which may be the same or different.</p> Signup and view all the answers

    What does the polymorphism in MHC genes refer to?

    <p>The presence of multiple different alleles for each isotype within a population.</p> Signup and view all the answers

    MHC Class II molecules are recognized by which type of T-cell receptors?

    <p>CD4+ helper T-cell receptors</p> Signup and view all the answers

    Which statement accurately reflects the expression of MHC proteins?

    <p>All nucleated cells in higher vertebrates express MHC proteins.</p> Signup and view all the answers

    What occurs to B cells after they leave the bone marrow?

    <p>They circulate through blood and lymph</p> Signup and view all the answers

    What is a consequence of the variability of MHC proteins in a population?

    <p>Greater difficulty in matching organ donors with recipients.</p> Signup and view all the answers

    What process ensures B cells do not have strong recognition of self before leaving the bone marrow?

    <p>Selection process</p> Signup and view all the answers

    What feature is common to heavy chain types in antibodies?

    <p>They determine antibody class</p> Signup and view all the answers

    What is the significance of combinatorial diversity in B cells?

    <p>It enables the creation of diverse antibodies</p> Signup and view all the answers

    What molecules do cytotoxic T cells primarily recognize?

    <p>MHC Class I molecules</p> Signup and view all the answers

    What is the first class of antibody secreted by a B-cell during an immune response?

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

    Which type of MHC molecule is recognized by CD8+ cytotoxic T-cells?

    <p>MHC Class I</p> Signup and view all the answers

    What role do TFH cells play in the B-cell response?

    <p>They help B-cells differentiate into plasma or memory cells.</p> Signup and view all the answers

    Which cells have MHC Class II molecules on their surface?

    <p>Dendritic cells, B-cells, and macrophages</p> Signup and view all the answers

    Where do long-lived plasma cells migrate to in order to provide a systemic source of antibodies?

    <p>Bone marrow</p> Signup and view all the answers

    What is required for B-cells to secrete antibodies?

    <p>Helper T-cell assistance</p> Signup and view all the answers

    Which statement best describes class switching of B-cells?

    <p>It changes the class of antibody the B-cell produces.</p> Signup and view all the answers

    What is the primary function of memory T-cells?

    <p>To remember past infections and respond quickly upon re-exposure</p> Signup and view all the answers

    What is the unique feature of inducible T cell costimulator (ICOS)?

    <p>It enhances B-cell responses.</p> Signup and view all the answers

    How does a T-cell receptor recognize an antigen?

    <p>When the antigen is presented by an MHC molecule</p> Signup and view all the answers

    What is the primary effect of MHC molecule heterogeneity on T-cell activation?

    <p>It allows a wider variety of peptides to be presented.</p> Signup and view all the answers

    What is the primary role of dendritic cells in T-cell activation?

    <p>To present antigens to T-cells.</p> Signup and view all the answers

    What happens to T-cells if they do not encounter their specific antigen?

    <p>They undergo apoptosis.</p> Signup and view all the answers

    Which characteristic is true for T-cell precursors in the thymus?

    <p>They do not express CD4 or CD8.</p> Signup and view all the answers

    How many MHC Class I allotypes can a typical individual express?

    <p>Up to 12</p> Signup and view all the answers

    What is the outcome of T-cell activation after encountering antigen presented by dendritic cells?

    <p>They proliferate and differentiate.</p> Signup and view all the answers

    What type of T-cells can help B-cells produce antibody molecules?

    <p>CD4+ T-cells</p> Signup and view all the answers

    What occurs when T-cells bind to antigens presented by dendritic cells?

    <p>They undergo signal transduction pathways leading to activation.</p> Signup and view all the answers

    What does seroconversion signify in the context of HIV infection?

    <p>The production of detectable antibodies.</p> Signup and view all the answers

    What role does the MHC play in the immune response?

    <p>It provides a mechanism for antigen presentation.</p> Signup and view all the answers

    How do cytotoxic T-cells engage with their targets?

    <p>By directly killing virus-infected cells.</p> Signup and view all the answers

    Why is MHC polymorphism important for population immunity?

    <p>It increases the diversity of antigen presentation.</p> Signup and view all the answers

    What happens to T-cells after they are continuously activated in lymph nodes?

    <p>They proliferate and can differentiate into effector cells.</p> Signup and view all the answers

    What initiates the signaling within a T-cell upon binding to a peptide:MHC complex?

    <p>Lck phosphorylation of ITAMs.</p> Signup and view all the answers

    Study Notes

    The Immune Response - Part 2

    • The adaptive immune response involves B-cells, T-cells, and dendritic cells.
    • Healthy skin is not inflamed.

    B-cells, T-cells and Dendritic cells

    • Surface wounds introduce bacteria, activating resident effector cells to secrete cytokines.
    • Vasodilation and increased vascular permeability allow fluid, proteins, and inflammatory cells to leave the blood and enter tissue.
    • The infected tissue becomes inflamed, causing redness, heat, swelling, and pain.
    • Macrophages engulf bacteria in infected tissue.
    • Afferent lymphatic vessels carry lymph from infected tissue.

    Phases of the Immune Response

    • Innate immune response: Inflammation, complement activation, phagocytosis, and pathogen destruction occur within minutes to days.
    • Adaptive immune response:
      • Antigen-presenting dendritic cells interact with antigen-specific T cells, promoting T-cell proliferation and differentiation (hours to days).
      • Antigen-specific B cells are activated (hours to days).
      • Effector and memory T cells are formed (days to weeks).
      • T cells interact with B cells, forming germinal centers and producing effector B cells (plasma cells) and memory B cells that produce antibody (days to weeks).
      • Effector lymphocytes emigrate from peripheral lymphoid organs (a few days to weeks).
    • Immunological memory: Maintenance of memory B and T cells with high antibody levels for protection against reinfection (days to weeks or lifelong).

    Antibodies

    • Antibodies are the secreted form of the BCR and are specific.
    • Antibodies bind to and neutralize bacterial toxins, viruses, and bacteria.
    • They coat pathogens (opsonization), promoting phagocytosis.
    • They activate complement (IgG and IgM).
    • Antibodies are highly folded, specific, and bind to epitopes to target pathogens.
    • Antibodies consist of two identical light chains (~25 kD) and two identical heavy chains (~50 kD or more).
    • Each light chain is joined to a heavy chain by a disulfide bond.
    • Each light chain/heavy chain dimer is connected by disulfide bonds.
    • Each light chain has a variable region and a constant region (of one domain).
    • Each heavy chain has a variable region and a constant region (of 3 or 4 domains).
    • Fab fragment (fragment antigen binding) is composed of light and part of a heavy chain.
    • Fc fragment (fragment crystalizable) is a portion of the heavy chain's constant region.
    • The Fc region of antibodies binds to Fc receptors on cells like macrophages.
    • Antibodies are the secreted form of the B-cell receptor and are specific for one antigen-binding site (epitope).

    Antibody Structure and Function

    • Antibodies consist of two identical light chains and two identical heavy chains, connected by disulfide bonds.
    • Each light chain has a variable region (VL) and a constant region (CL).
    • Each heavy chain has a variable region (VH) and constant region(s) (CH).
    • The six hypervariable regions (CDRs) form the antigen-binding site.
    • Two light chains and two heavy chains combine to form the antibody structure.
    • Different classes of antibodies (IgM, IgG, IgA, IgE, IgD) have distinct roles.

    Generation of B Cell Antigen Recognition Diversity

    • Step 1: Somatic Recombination: Generates the variable regions in light and heavy chains.
      • Light chain: Joins one V segment and one J segment.
      • Heavy chain: Joins one V, one D, and one J segment.
    • Step 2: Junctional Diversity: Adds new and random nucleotides at V and J segments.
    • Step 3: Combinatorial Diversity: Combines the variable regions.
    • B-cells in bone marrow produce heavy chain first, followed by light chain, then undergo specific selection.

    What happens when B and T cells leave the bone marrow

    • B cells circulate between blood and lymph.
    • B cells phagocytose antigen in lymph node.
    • B cells require T cell help to secrete antibody.
    • B cells process antigen to present on their surface in context of MHC molecule.

    T Cell Structure and Function

    • Helper T cells (CD4+): Regulate other white blood cells.
    • Cytotoxic T cells (CD8+): Kill virus-infected cells.
    • Regulatory T cells: Suppress the immune response.
    • T helper cells help activate macrophages, B cells and cytotoxic T Cells.
    • T cell precursors develop in thymus from bone marrow.
    • CD4+ or CD8+ T-cells mature in thymus and emerge.
    • Naive T cells circulate between blood and lymph.
    • T cells recognize antigen complexes on antigen presenting cells.
    • T cells are activated in lymph nodes.
    • When activated, T cells proliferate and differentiate.

    MHC Molecules

    • MHC molecules present antigens to T cells.
    • Class I MHC molecules are on all nucleated cells and present endogenous antigens.
    • Class II MHC molecules are on antigen-presenting cells and present exogenous antigens.

    Antigen Processing and Presentation

    • Pathogen pieces are bound to MHC class I or II molecules.
    • MHC molecules present antigen fragments on cell surfaces.

    T-cell Receptor Function

    • The T-cell receptor recognizes antigen only when presented by an MHC molecule.
    • CD4 binds to the B2 domain of MHC II.
    • CD8 binds to the α3 domain of MHC I.

    Effector Functions of T Cells

    • Cytotoxic T cells kill virus-infected cells.
    • Helper T cells activate macrophages, B cells, and other components of the immune system.

    B-cell Differentiation and Antibody Production

    • TFH cells determine if B cells become plasma or memory cells, and help activate B cells.

    Antibody Response

    • The primary response to an antigen produces IgM first.
    • The secondary response is faster and stronger because of immunological memory.

    Summary

    • Different cell types and actions work together during immune response.
    • Helper T cells play a critical role in activating B-cells and other immune responses.
    • Antibody responses vary based on mechanisms of recognition and binding to antigens, leading to diverse and adaptive responses.

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    Chapter 17.2: The Immune Response (PDF)

    Description

    Dive deeper into the adaptive immune response, focusing on B-cells, T-cells, and dendritic cells. This quiz covers the phases of the immune response, mechanisms like phagocytosis, and the role of inflammation. Test your understanding of these crucial immune functions.

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