Immunology 2
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Questions and Answers

What is the primary mechanism that distinguishes the initiation of the Classical Pathway from the other complement pathways?

  • Binding of antibodies to the pathogen’s surface (correct)
  • Formation of the antigen-antibody complex
  • Utilization of regulatory proteins for activation
  • Activation by polysaccharides on pathogen

    • How does the regulatory network function in the context of the complement system?

  • Facilitates constant activation of complement
  • Enhances the formation of antigen-antibody complexes
  • Minimizes tissue repair processes
  • Terminates complement activity to prevent tissue damage (correct)

    • Which step occurs after the formation of the antigen-antibody complex in the Classical Pathway?

  • Activation of C1 following antigen binding (correct)
  • Formation of C2a and C4b without C1
  • Direct splitting of C2 and C4
  • Binding of C2 and C4 to the antibody

    • What is the role of activated C1 in the Classical Pathway?

    <p>It activates C2 and C4 by splitting them</p> Signup and view all the answers

    Which of the following statements is true regarding the regulatory proteins in the complement pathways?

    <p>They block activation of C1 in all three pathways</p> Signup and view all the answers

    What is the primary function of B cells in the immune system?

    <p>To produce antibodies against specific antigens</p> Signup and view all the answers

    Where do T cells undergo differentiation?

    <p>In the thymus</p> Signup and view all the answers

    Which type of lymphoid tissue is involved in gut-associated immunity?

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

    What are antibodies also known as?

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

    What happens to mature lymphocytes after processing in primary lymphoid tissues?

    <p>They migrate to secondary lymphoid tissues</p> Signup and view all the answers

    What is the role of antibodies in adaptive immunity?

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

    Which statement about the lymphatic system is correct?

    <p>Lymphocytes interact with antigens in secondary lymphoid organs</p> Signup and view all the answers

    Which of the following is NOT a secondary lymphoid organ?

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

    What is the primary function of CD8 T cells?

    <p>To eliminate body cells infected with intracellular organisms</p> Signup and view all the answers

    Which type of T cell is primarily associated with the regulation of immune responses?

    <p>T reg</p> Signup and view all the answers

    What feature is unique to immature B cells?

    <p>They express IgM and IgD on their surface</p> Signup and view all the answers

    What triggers apoptosis in infected cells?

    <p>Cytotoxic action of CD8 T cells</p> Signup and view all the answers

    What is the primary role of B cells in humoral immunity?

    <p>To mediate antibody production</p> Signup and view all the answers

    Which type of T cell is involved in the activation of B cells?

    <p>Th2 cells</p> Signup and view all the answers

    What characteristic distinguishes a B cell receptor (BCR)?

    <p>It responds only to specific antigens or closely related groups</p> Signup and view all the answers

    Which T cell subtype is known for their role in generating an inflammatory response?

    <p>Th1 cells</p> Signup and view all the answers

    What occurs to infected cells before any significant leakage occurs?

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

    What is a key factor contributing to the complexity of immune function?

    <p>Lymphocytes working closely with macrophages</p> Signup and view all the answers

    What is the first step in B cell activation when an antigen is present?

    <p>BCR of the B cell binds to the antigen</p> Signup and view all the answers

    Which cells are primarily responsible for producing antibodies?

    <p>Plasma cells</p> Signup and view all the answers

    What is the function of memory cells after an infection has resolved?

    <p>They continue to circulate in the host</p> Signup and view all the answers

    During the primary immune response, which immunoglobulin is produced first?

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

    What process involves the selection of lymphocytes that will multiply in clones?

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

    How many antibody molecules can a plasma cell produce per second?

    <p>2,000</p> Signup and view all the answers

    What happens to plasma cells after the infection is over?

    <p>They die out</p> Signup and view all the answers

    What characterizes the primary immune response in terms of time taken to fully develop?

    <p>1-2 weeks</p> Signup and view all the answers

    What is the main role of BCR in B cell function?

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

    Which cells are formed after B cells undergo clonal selection?

    <p>Both plasma and memory cells</p> Signup and view all the answers

    What is the primary function of antibodies in the process of opsonization?

    <p>To coat the pathogen, enhancing its phagocytosis</p> Signup and view all the answers

    How do antibodies neutralize toxins?

    <p>By blocking their active sites</p> Signup and view all the answers

    What is an effect of antibody-dependent cell-mediated cytotoxicity (ADCC)?

    <p>Binding of antibodies to target cells leading to their destruction</p> Signup and view all the answers

    Which pathway enhances phagocytosis through opsonization?

    <p>Classical Pathway</p> Signup and view all the answers

    What role do eosinophils play in the immune response?

    <p>Binding to antibodies via Fc region receptors</p> Signup and view all the answers

    What is the result of the antibodies coating the surface of a pathogen?

    <p>It promotes the pathogen's susceptibility to phagocytosis</p> Signup and view all the answers

    Which of the following processes can eliminate large parasites?

    <p>Antibody-dependent cell-mediated cytotoxicity</p> Signup and view all the answers

    Which statement describes the mechanism of the classical pathway in immunity?

    <p>It enhances opsonization through antibody binding</p> Signup and view all the answers

    What occurs when antibodies coat microorganisms?

    <p>They block the adhesion of bacteria and viruses to mucosa</p> Signup and view all the answers

    What is the primary location where B cells develop in adults?

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

    What happens to B cells after they mature?

    <p>They migrate to lymphoid organs.</p> Signup and view all the answers

    Which process involves B cells dividing into many clones upon encountering an antigen?

    <p>Clonal selection</p> Signup and view all the answers

    What type of cells actively secrete antibodies?

    <p>Plasma cells</p> Signup and view all the answers

    What is the primary function of immunogens in the immune system?

    <p>To elicit immune responses</p> Signup and view all the answers

    What role do T cells play in the immune response?

    <p>Cell-mediated immunity</p> Signup and view all the answers

    Which component is NOT considered a key player in adaptive immunity?

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

    What is the term for the production of antibodies by activated B cells?

    <p>Humoral immunity</p> Signup and view all the answers

    What type of immunity is primarily associated with the function of antibodies?

    <p>Humoral immunity</p> Signup and view all the answers

    What distinguishes adaptive immunity from innate immunity?

    <p>It can remember specific pathogens for faster response upon re-exposure</p> Signup and view all the answers

    What role do antibodies play in the immune response?

    <p>They bind to pathogens to neutralize or mark them for destruction</p> Signup and view all the answers

    Which lymphoid organs are crucial for B cell activation and response?

    <p>Lymph nodes and spleen</p> Signup and view all the answers

    Which of the following best describes the response of acquired immunity?

    <p>Delayed but highly specific</p> Signup and view all the answers

    What initiates the clonal selection process in B cells?

    <p>Encountering a foreign antigen</p> Signup and view all the answers

    What do activated B cells primarily differentiate into?

    <p>Plasma cells</p> Signup and view all the answers

    What is the primary significance of determining blood types in the context of adaptive immunity?

    <p>To facilitate organ matching for transplants</p> Signup and view all the answers

    How do antigens interact with antibodies in the immune system?

    <p>Antibodies bind to specific sites on antigens called epitopes</p> Signup and view all the answers

    What is the function of the complement system in adaptive immunity?

    <p>Enhancing the ability of antibodies and phagocytes to clear pathogens</p> Signup and view all the answers

    What type of disorders is associated with deficiencies in C1, C2, or C4 complement molecules?

    <p>Collagen vascular disorders</p> Signup and view all the answers

    Which complement deficiency is particularly associated with increased susceptibility to infections?

    <p>C3, C2</p> Signup and view all the answers

    What infectious diseases are associated with deficiencies in C5 to C9 complement components?

    <p>Neisseria meningitidis and N. gonorrhoeae</p> Signup and view all the answers

    Which cells are predominantly responsible for expressing Class II molecules?

    <p>Macrophages and Dendritic cells</p> Signup and view all the answers

    Which complements are encoded by HLA-D region's genes?

    <p>HLA-DP, HLA-DQ, HLA-DR</p> Signup and view all the answers

    Which class of molecules do CD8 T-cells primarily interact with?

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

    What is a likely consequence of complement deficiencies?

    <p>Increased susceptibility to various infections</p> Signup and view all the answers

    Which type of cell does NOT express Class I molecules?

    <p>Muscle cells</p> Signup and view all the answers

    What specific role do Class III molecules play in the immune system?

    <p>They encode complement proteins and cytokines.</p> Signup and view all the answers

    What is the primary role of Helper T Cells in cell-mediated immunity?

    <p>Activate macrophages and assist in B-cell processes</p> Signup and view all the answers

    Which of the following statements is true regarding cytotoxic T cells?

    <p>They destroy infected host cells and foreign cells.</p> Signup and view all the answers

    What must occur for T-cells to recognize an antigen?

    <p>The antigen must be presented by MHC on an antigen-presenting cell.</p> Signup and view all the answers

    Which statement accurately describes the Major Histocompatibility Complex (MHC)?

    <p>It enables T cells to distinguish self from non-self.</p> Signup and view all the answers

    What distinguishes adaptive immunity from innate immunity in regards to cellular components involved?

    <p>Adaptive immunity primarily involves T-lymphocytes and antigen processing.</p> Signup and view all the answers

    What is the role of MHC Class I proteins in antigen presentation?

    <p>They present antigens to T cells for recognition.</p> Signup and view all the answers

    Which immunoglobulin is predominantly present on the surface of immature B cells?

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

    What triggers the activation of B cells?

    <p>Binding of specific antigens to B-cell receptors.</p> Signup and view all the answers

    What is the outcome of the interaction between B cells and T cells?

    <p>Production of antibodies by activated B cells.</p> Signup and view all the answers

    How does an antigen interact with B cells?

    <p>By fitting into a specific BCR, triggering a response.</p> Signup and view all the answers

    What initiates the process of antigen presentation by an antigen-presenting cell (APC)?

    <p>Capture and processing of exogenous antigens.</p> Signup and view all the answers

    Which statement accurately describes how antigens are recognized by T cells?

    <p>Antigens must be attached to MHC molecules of an APC.</p> Signup and view all the answers

    What is the primary function of the groove in MHC molecules?

    <p>To hold and present antigen fragments.</p> Signup and view all the answers

    What is the main characteristic of B-cell receptors (BCRs)?

    <p>They can bind to a specific antigen or a related group.</p> Signup and view all the answers

    What is the consequence of a B cell successfully binding to an antigen?

    <p>Clonal expansion and differentiation.</p> Signup and view all the answers

    Study Notes

    Lymphocytes Overview

    • Two primary types of lymphocytes: B cells and T cells.
    • B cells differentiate and mature in the bone marrow; T cells do so in the thymus.
    • Mature lymphocytes migrate to secondary lymphoid organs for antigen interaction.

    Antibodies

    • Antibodies, or immunoglobulins, are produced in response to specific epitopes on pathogens.
    • They help in the inactivation or destruction of infectious agents.
    • Antibodies can be found in blood serum, body fluids, and tissues, and are highly specific.

    Humoral Immunity

    • Characterized by antibody-mediated responses primarily involving B cells.
    • Immature B cells express IgM and IgD on their surface as receptors.

    B Cell Function

    • B cell receptors (BCR) specifically respond to individual antigens.
    • Activated B cells can proliferate into plasma cells and memory cells; the latter ensures long-term immunity.
    • Plasma cells can produce up to 2,000 antibody molecules per second.

    Antibody Actions

    • Antibodies function through various mechanisms, including neutralization and opsonization.
    • Neutralization involves blocking toxin and pathogen action.
    • Opsonization enhances pathogen phagocytosis by coating them with antibodies.

    Antibody-Dependent Cell-Mediated Cytotoxicity (ADCC)

    • Involves destruction of target cells (e.g., large parasites) via non-specific immune cells.
    • Eosinophils, macrophages, and NK cells bind to antibodies on target cells, releasing enzymes to damage them.

    Pathways of Antibody Action

    • Classical pathway initiated by the binding of antibodies to antigens, forming a complex that activates C1 and leads to further complements.
    • Complement pathways (Classical, Alternative, Lectin) differ by their initiation mechanism but converge on enhancing immune response.

    Clonal Selection and Memory

    • Clonal selection process ensures that only lymphocytes specific to an antigen are activated and reproduce.
    • Initial B cell response to infection takes about 1-2 weeks, with IgM being the first immunoglobulin produced.
    • After the infection, plasma cells die, but memory cells persist for quicker responses upon re-exposure.

    Regulation of Complement Pathway

    • Serum regulatory proteins control the complement system, preventing excessive activation and tissue damage.
    • Regulation occurs at multiple stages to ensure that complement activity is appropriately terminated.

    Adaptive Immunity

    • Represents the body's third line of defense against pathogens.
    • Enables recognition and response to specific invaders and products, such as protozoa, fungi, bacteria, viruses, or toxins.
    • Referred to as acquired or specific immunity, activated when innate immunity is compromised.

    Key Players & Components

    • Antibodies: Proteins generated to neutralize antigens.
    • Antigens: Substances that elicit an immune response (immunogens).
    • Lymphocytes: White blood cells, including B-cells and T-cells, essential for adaptive immunity.
    • Cytokines: Signaling proteins that mediate and regulate immunity.
    • Complement System: Proteins that enhance the immune response, assisting in the elimination of pathogens.

    Cell Activation

    • B-Cell Receptors (BCRs): Immunoglobulin receptors on B-cells that recognize specific antigens, generally IgM and sometimes IgD.
    • Interaction between B-cells and T-cells occurs in lymphoid organs such as lymph nodes and the spleen.

    Major Adaptive Immune Responses

    • Humoral: Mediated by antibodies circulating in body fluids.
    • Cell-Mediated: Carried out by T-cells at a cellular level.

    B-Cell Activation Mechanism

    • Clonal selection occurs when a B-cell encounters a specific antigen, leading to proliferation into plasma cells that produce antibodies.

    Complement System & Diseases

    • Deficiencies in complement proteins can increase susceptibility to infections.
    • Specific deficiencies correlated with clinical conditions, such as:
      • C1, C2, or C4: Linked to collagen vascular disorders.
      • C3, C2: Higher infection susceptibility.
      • C5 to C9: Increased risk of infections from Neisseria species.

    Cell-Mediated Immunity

    • Provides defense against intracellular microbes and infections that antibodies cannot address.
    • Mediated by T-lymphocytes, crucial for recognizing antigens from infected cells.

    Components of Cell-Mediated Immune System

    • Helper T Cells (CD4): Activate macrophages, assist B-cell activation, and cytotoxic T-cell activation.
    • Cytotoxic T Cells (CD8): Responsible for destroying infected host cells and foreign cells.

    Immune Response Mechanism

    • An effective immune response requires distinguishing between self and non-self.
    • Innate Immunity: Utilizes toll-like receptors (TLRs) to detect microbial components.
    • Adaptive Immunity: Involves identification, processing, and presentation of antigens using:
      • Antibody-antigen Complex: Direct binding of antigens to antibodies.
      • Major Histocompatibility Complex (MHC): Essential for T-cells to recognize peptide antigens presented by antigen-presenting cells (APCs).

    Major Histocompatibility Complex (MHC)

    • Also known as the Human Leukocyte Antigen (HLA) system; crucial receptors on lymphocytes and macrophages.
    • Differentiated into Class I MHC (present on most nucleated cells) and Class II MHC (found mainly on APCs), both key for proper immune function.

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    Description

    Test your knowledge on the two main types of lymphocytes: B cells and T cells. This quiz will cover the characteristics, functions, and roles of these vital components of the immune system. Understand how they contribute to antigen-specific responses.

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