Humoral Immunity and Antibodies - 2.2
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Questions and Answers

What roles do antibodies play in the immune response?

  • They directly kill pathogens by lysis.
  • They only function as receptors on B-cells.
  • They neutralize toxins and enhance phagocytosis. (correct)
  • They promote apoptosis and activate cytokines.

    • What is the function of the Fab region of an antibody?

  • Binds to Fc receptors on immune cells.
  • Identifies and binds to antigens. (correct)
  • Remains constant throughout the immune response.
  • Promotes apoptosis of infected cells.

    • Which process describes the alteration of B-cell antibody isotype production in response to T-helper cell cytokines?

  • Somatic hypermutation
  • Clonal selection
  • Class switching (correct)
  • Affinity maturation

    • What is a key feature of the IgG antibody?

    <p>It can cross the placenta and provide passive immunity.</p> Signup and view all the answers

    Which statement about somatic hypermutation is true?

    <p>It leads to increased variability in antibody production.</p> Signup and view all the answers

    What is the result of opsonization in the immune response?

    <p>Enhanced recognition and engulfment by phagocytes.</p> Signup and view all the answers

    Which antibody is primarily involved in passive immunity through breast milk?

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

    Which immune response is characterized by the rapid production of antibodies after a secondary exposure to an antigen?

    <p>Secondary immune response</p> Signup and view all the answers

    Which statement correctly describes the role of antibodies in humoral immunity?

    <p>Antibodies facilitate opsonization and enhance phagocytosis.</p> Signup and view all the answers

    What accurately describes the structure of antibodies?

    <p>The Fab region is responsible for binding to antigen epitopes.</p> Signup and view all the answers

    What is the primary mechanism through which antibodies neutralize toxins?

    <p>By blocking receptors on target cells from interacting with toxins.</p> Signup and view all the answers

    Which statement most accurately describes passive immunity?

    <p>It primarily results from the transfer of antibodies through the placenta or breast milk.</p> Signup and view all the answers

    What is implied by class switching in B-cells?

    <p>B-cells switch the isotype of antibodies they produce based on cytokine signals.</p> Signup and view all the answers

    Which mechanism directly mediates antibody-dependent cell cytotoxicity (ADCC)?

    <p>Natural killer cells recognize and destroy antibody-coated target cells.</p> Signup and view all the answers

    What is a consequence of somatic hypermutation in B-cells?

    <p>It influences the affinity of antibodies for their specific antigens.</p> Signup and view all the answers

    How do secretory IgA antibodies function in mucosal immunity?

    <p>They neutralize pathogens by blocking their attachment to epithelial cells.</p> Signup and view all the answers

    What percentage of IgG antibodies are found within blood plasma and extracellular fluids?

    <p>65-70%</p> Signup and view all the answers

    What type of immunity do IgG antibodies provide to the baby from the mother?

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

    What form do secretory IgA antibodies take?

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

    Where can IgA antibodies be found in the body?

    <p>In sweat and saliva</p> Signup and view all the answers

    What is the primary function of IgM antibodies?

    <p>Binding to pathogens in the early immune response</p> Signup and view all the answers

    What type of structure characterizes IgM antibodies?

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

    What is the primary cell type responsible for secreting antibodies?

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

    What causes IgA antibodies to be effective in mucosal defenses?

    <p>Their dimeric structure</p> Signup and view all the answers

    Which percentage of IgG antibodies is typically found in blood plasma?

    <p>65 to 70 percent</p> Signup and view all the answers

    What type of structure do IgG antibodies have?

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

    What beneficial feature do IgA antibodies provide through breast milk?

    <p>Immediate passive immunity</p> Signup and view all the answers

    During which immune response are IgG antibodies produced in greater abundance?

    <p>Secondary immune response</p> Signup and view all the answers

    Which antibody type is most abundant during the secondary immune response?

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

    What mechanism allows IgG antibodies to enhance complement proteins?

    <p>Membrane attack complex</p> Signup and view all the answers

    Which mechanism describes the process where antibodies bind free antigens to enhance phagocytosis?

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

    In which fluid types are IgA antibodies predominantly found?

    <p>Saliva and secretions in the GI tract</p> Signup and view all the answers

    What happens when IgG antibodies bind to a virus particle?

    <p>They neutralize the virus and prevent host cell infection.</p> Signup and view all the answers

    Which of the following processes do IgG antibodies NOT participate in?

    <p>Infection promotion</p> Signup and view all the answers

    What is the role of IgG antibodies in relation to viruses?

    <p>Binding and causing neutralization</p> Signup and view all the answers

    Which antibody is notably involved in defense against gastrointestinal bacteria?

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

    What is the term for the complex formed when complement proteins are activated by antibodies?

    <p>Membrane attack complex</p> Signup and view all the answers

    What role do plasma cells play in antibody production?

    <p>They secrete antibodies.</p> Signup and view all the answers

    Which type of immunity is primarily provided by IgG antibodies from the placenta to a fetus?

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

    What is the likely consequence of a deficiency in IgG antibody production?

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

    What happens during opsonization in the context of IgG antibodies?

    <p>Antibodies facilitate the digestion of pathogens by phagocytes.</p> Signup and view all the answers

    Which characteristic of IgG antibodies enhances inflammation by interacting with complement proteins?

    <p>C3 and C5a activation</p> Signup and view all the answers

    How do IgG antibodies contribute to the immune response when encountering a new antigen?

    <p>They are produced in higher amount during subsequent encounters with the same antigen.</p> Signup and view all the answers

    What is the function of the Fc epsilon r1 receptor on mast cells?

    <p>It binds to monomeric IgE antibodies in response to allergens.</p> Signup and view all the answers

    What immediate effect does the binding of IgE antibodies to mast cells have?

    <p>Triggers the release of inflammatory chemicals.</p> Signup and view all the answers

    What occurs during an anaphylactic reaction related to airway constriction?

    <p>Smooth muscle contraction reduces airway size.</p> Signup and view all the answers

    What role do leukotrienes play in allergic reactions?

    <p>They cause widespread vasodilation and increased capillary permeability.</p> Signup and view all the answers

    What can result from increased capillary permeability in the respiratory mucosa?

    <p>Development of edema and airway obstruction.</p> Signup and view all the answers

    Which antibody is primarily involved in the immune response to parasitic infections?

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

    What is the primary consequence of histamine release from mast cells?

    <p>Increased airway resistance due to bronchoconstriction.</p> Signup and view all the answers

    How do eosinophils contribute to the immune response to parasites?

    <p>They release proteins that damage parasitic membranes.</p> Signup and view all the answers

    What type of hypersensitivity reaction is primarily associated with anaphylaxis?

    <p>Type I hypersensitivity.</p> Signup and view all the answers

    What is the primary role of IgD antibodies in the immune response?

    <p>Enhancing B cell activation and differentiation.</p> Signup and view all the answers

    What happens to airway size when smooth muscle cells in the bronchi contract?

    <p>Airway size decreases, limiting airflow.</p> Signup and view all the answers

    Why is persistent exposure to allergens potentially dangerous?

    <p>It can contribute to chronic inflammation and tissue damage.</p> Signup and view all the answers

    What outcome is associated with the action of inflammatory mediators like prostaglandins during an allergic response?

    <p>Increased vascular permeability and inflammatory response.</p> Signup and view all the answers

    What is the function of disulfide bonds in the structure of antibodies?

    <p>They help to maintain the three-dimensional structure of the antibody.</p> Signup and view all the answers

    What distinguishes IgM antibodies from other classes of antibodies during an immune response?

    <p>They are the first antibodies produced during a primary immune response.</p> Signup and view all the answers

    How do variable heavy and light chains contribute to antibody specificity?

    <p>They undergo recombination to form distinct antigen-binding sites.</p> Signup and view all the answers

    What is one major role of IgM antibodies concerning foreign antigens?

    <p>They activate the complement system.</p> Signup and view all the answers

    What is the total number of antigen-binding sites present in an IgM antibody?

    <p>Five binding sites as a pentamer.</p> Signup and view all the answers

    Which of the following processes describes what happens when IgM antibodies bind to mismatched blood during transfusion?

    <p>Agglutination occurs.</p> Signup and view all the answers

    What feature distinguishes the variable regions of antibodies?

    <p>They vary between different antibody types to accommodate different antigens.</p> Signup and view all the answers

    What type of hypersensitivity is associated with mismatched blood transfusions involving IgM antibodies?

    <p>Type 2 hypersensitivity</p> Signup and view all the answers

    Why is it significant that antibodies have two antigen-binding sites?

    <p>It enhances their ability to cross-link antigens.</p> Signup and view all the answers

    Which characteristic is true for IgE antibodies?

    <p>They can trigger an anaphylactic shock.</p> Signup and view all the answers

    What role do variable regions specifically play in the immune response?

    <p>They allow for the differentiation between friend and foe.</p> Signup and view all the answers

    Where are IgE antibodies primarily found within the body?

    <p>Within mucosal tissues and lymphatic tissues.</p> Signup and view all the answers

    In terms of antibody structure, what does the term 'constant region' refer to?

    <p>The part of the antibody that remains the same across different types.</p> Signup and view all the answers

    How many antigen-binding sites does a pentameric IgM antibody possess?

    <p>10</p> Signup and view all the answers

    What characteristic of antibodies allows them to bind effectively to foreign invaders?

    <p>The unique conformation of their variable regions.</p> Signup and view all the answers

    Which condition could indicate that a person is undergoing a primary immune response based on antibody levels?

    <p>Elevated levels of IgM antibodies.</p> Signup and view all the answers

    What common function do both IgM and IgE antibodies share?

    <p>They are produced by plasma cells.</p> Signup and view all the answers

    What is the role of the complement system when activated by IgM antibodies?

    <p>To enhance phagocytosis and promote cell lysis.</p> Signup and view all the answers

    How does the structure of IgM antibodies contribute to their function?

    <p>Their pentameric structure allows for binding to multiple antigens.</p> Signup and view all the answers

    Which of the following best describes the physiological importance of IgM antibodies during an infection?

    <p>They provide immediate response to initial infection.</p> Signup and view all the answers

    Which antibody type is predominantly involved in allergic responses?

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

    What specific tissues or areas are IgE antibodies primarily associated with?

    <p>Mucosal surfaces and lymphatic tissues</p> Signup and view all the answers

    What occurs first during the primary immune response to an antigen?

    <p>Production of IgM antibodies</p> Signup and view all the answers

    What is indicated by the term 'somatic hypermutation' in the context of immune response?

    <p>A change in the genetic sequence of B-cells to produce IgG antibodies</p> Signup and view all the answers

    During the secondary immune response, which antibody is primarily produced?

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

    Which phase of the immune response is characterized by a delay before antibody production begins?

    <p>Primary response</p> Signup and view all the answers

    What initiates the switch from producing IgM antibodies to IgG antibodies in B-cells?

    <p>Cytokines and interleukins</p> Signup and view all the answers

    What happens to the levels of IgM during the secondary immune response?

    <p>IgM levels decrease but are still produced</p> Signup and view all the answers

    Which of the following best describes the timeline of antibody production after first exposure to an antigen?

    <p>Lag period, then IgM production peaks, followed by IgG</p> Signup and view all the answers

    In the context of B-cell activation, what role do microbes play?

    <p>They can trigger the production of specific types of antibodies</p> Signup and view all the answers

    What defines the relationship between IgM and IgG during the immune response?

    <p>IgM is produced first and then primarily IgG follows</p> Signup and view all the answers

    What characterizes the 'lag period' observed after antigen exposure?

    <p>Time taken for plasma cells to start antibody production</p> Signup and view all the answers

    How does cytokine signaling influence the production of antibodies in B-cells?

    <p>Cytokines can induce isotype switching from IgM to IgG</p> Signup and view all the answers

    What is the function of the B-cell receptor in the immune response?

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

    What can happen to IgG levels during repeated antigen exposure?

    <p>IgG production rises significantly compared to the initial response</p> Signup and view all the answers

    What distinguishes passive immunity from active immunity?

    <p>Active immunity results from direct exposure to an antigen.</p> Signup and view all the answers

    Which example represents naturally acquired passive immunity?

    <p>Antibodies passed from mother to fetus through the placenta.</p> Signup and view all the answers

    What is an example of artificially acquired active immunity?

    <p>Vaccination with a weakened pathogen.</p> Signup and view all the answers

    Why is the administration of antivenom considered a form of passive immunity?

    <p>It introduces antibodies that were not produced by the recipient's body.</p> Signup and view all the answers

    Which type of immunity is characterized by the production of antibodies as a direct response to infection?

    <p>Active natural immunity.</p> Signup and view all the answers

    What role does somatic hypermutation play in antibody production?

    <p>It enhances the diversity of antibodies to better target specific antigens.</p> Signup and view all the answers

    In terms of antibody structure, what is the function of the constant heavy chain?

    <p>It determines the class of the antibody.</p> Signup and view all the answers

    What is a common misconception about artificially acquired passive immunity?

    <p>It involves the creation of antibodies by the host.</p> Signup and view all the answers

    Which of the following correctly describes artificially acquired passive immunity?

    <p>Receiving immunoglobulins after a snake bite.</p> Signup and view all the answers

    What is the major difference between naturally acquired and artificially acquired active immunity?

    <p>Naturally acquired involves direct exposure to antigens, whereas artificially acquired involves vaccinations.</p> Signup and view all the answers

    What is the main misconception about antibodies derived from maternal sources?

    <p>They are responsible for providing lifelong immunity.</p> Signup and view all the answers

    What mechanism enables vaccines to provide long-lasting protection?

    <p>Introducing a weak or dead pathogen to induce an immune response.</p> Signup and view all the answers

    How does the structure of antibodies contribute to their function?

    <p>The variable region contains all the necessary information to produce antibodies.</p> Signup and view all the answers

    What is the relationship between somatic hypermutation and the production of IgG antibodies during secondary responses?

    <p>Somatic hypermutation increases the specificity of IgG antibodies after re-exposure.</p> Signup and view all the answers

    Study Notes

    Humoral Immunity and Antibodies

    • Humoral immunity is a type of adaptive immunity that involves antibodies produced by B cells.
    • Key components include:
      • Complement system
      • Antibodies (AB)
      • B cells and plasma cells
      • Cytokines and chemokines
    • An epitope is a specific part of an antigen (AG) recognized by an antibody.
    • B cell receptor (BCR) is an antibody attached to a B cell.
    • Antibodies are called immunoglobulins (Ig) when free-floating in the body.
    • Lymph nodes are important sites for B cell activation and antibody production.

    B-cell Development

    • B cell development involves stages of differentiation, starting with a progenitor B cell before becoming a mature B cell.
    • B cell development consists of two stages:
      • Antigen-independent stage:
        • Pro-B cell formation
        • Pre-B cell formation
        • Immature B cell formation
        • Mature B cell formation
      • Antigen-dependent stage:
        • Activation of B cells by antigens
        • Differentiation into antibody-producing plasma cells
        • Memory B cell formation

    Humoral Immunity

    • Humoral immunity is an essential component of the adaptive immune system.
    • It involves the production of antibodies by B cells in response to antigen exposure.
    • The main functions of humoral immunity involve:
      • Antibody production: B cells differentiate into plasma cells that produce antibodies.
      • Antigen recognition: Antibodies bind specifically to antigens, targeting them for destruction.
      • Neutralization: Blocking the activity of pathogens by binding to their surface receptors.
      • Opsonization: Coating pathogens with antibodies, enhancing phagocytosis by macrophages.
      • Complement activation: Antibodies activate the complement cascade leading to pathogen lysis and inflammation.
      • Memory response: B cells generate memory cells that rapidly mount a response upon re-exposure to the same antigen.

    Antibodies (Immunoglobulins)

    • Antibodies are Y-shaped proteins composed of four polypeptide chains: two heavy chains and two light chains.
    • They have a constant region (Fc region) and a variable region (Fab region).
    • The Fc region binds to Fc receptors on immune cells, while the Fab region binds to antigens.
    • Antibodies are classified into five major isotypes:
      • IgG: The most abundant in serum, plays a key role in opsonization, complement activation, and neutralization.
      • IgA: Found primarily in mucosal secretions, like saliva, tears, and breast milk, protects against pathogens entering the body.
      • IgM: First antibody produced during an immune response, good at activating complement.
      • IgE: Involved in allergic reactions, binds to mast cells and basophils, triggering the release of histamine.
      • IgD: Its exact function is not fully understood, found on the surface of B lymphocytes, may be involved in B cell activation.
    • B cells undergo class switching to produce different antibody isotypes depending on the nature of the infection and the presence of specific cytokines.
    • Somatic hypermutation occurs to increase the diversity of antibody binding sites.
    • Passive immunity is acquired by receiving antibodies from an external source, such as through the placenta or through injections.
    • Active immunity is acquired through exposure to an antigen, either through infection or vaccination.

    Antibody Diversity

    • Antibody diversity is achieved through a complex process of gene rearrangement and somatic hypermutation.
    • This diversity allows the immune system to recognize and respond to a vast array of antigens.
    • The process of antibody binding involves the variable (V), diversity (D), and joining (J) gene segments.
    • Different combinations of these segments lead to a wide range of variable regions.

    Functions of Antibodies

    • Antibodies perform a variety of functions in the immune system.
    • Neutralization: Antibodies prevent pathogens from entering cells or binding to their targets.
    • Opsonization: Antibodies coat pathogens, making them more easily recognized and engulfed by phagocytes (cells that engulf and destroy pathogens).
    • Complement Activation: Antibodies activate the complement system, a cascade of proteins that can lyse pathogens.
    • Antibody-dependent cell cytotoxicity (ADCC): Antibodies can bind to target cells and recruit NK cells to kill them.

    Antibody-mediated Immunity in Parasitic Infections

    • Antibodies are crucial against parasitic infections.
    • They help to neutralize parasites, prevent their entry into cells, and enhance their clearance by immune cells.
    • Some antibodies, like IgA, are particularly important in mucosal immunity, protecting against parasitic infections at mucosal surfaces.

    Transport of IgA Across Mucosal Epithelium

    • IgA is produced by plasma cells located in mucosal tissues and is transported across the epithelium by a process called transcytosis.
    • This process allows IgA to reach the mucosal surfaces where it can neutralize pathogens.

    Antibody-dependent Cell Cytotoxicity (ADCC)

    • This process involves the collaboration of antibodies and natural killer (NK) cells to eliminate infected or abnormal cells.
    • Steps of ADCC:
      • Antibodies bind to antigens on the surface of target cells.
      • NK cells express Fc receptors that recognize the bound antibodies.
      • Binding activates NK cells, triggering the release of cytotoxic molecules, leading to the death of the target cell.

    Mast Cell Degranulation

    • Activated mast cells release granules containing inflammatory mediators, such as histamine, that trigger allergic reactions.

    Antibodies in the Oral Cavity

    • Saliva and gingival crevicular fluid (GCF) contain antibodies that contribute to oral health.
    • Saliva:
      • Contains IgA against bacteria and viruses.
      • Plays a role in inhibiting plaque formation and reducing bacterial adhesion to teeth.
    • Gingival Crevicular Fluid:
      • Contains IgG and IgA, which target oral pathogens and may contribute to the defense against periodontal disease.
      • Has the ability to stimulate immune responses that lead to inflammation and infection clearance.

    Autoimmune Diseases

    • Graves' Disease:
      • An autoimmune disorder where antibodies target the thyroid-stimulating hormone receptor, leading to overproduction of thyroid hormones.
      • Symptoms:
        • Hyperthyroidism
        • Rapid heartbeat
        • Weight loss
        • Tremors
        • Fatigue
        • Protruding eyes (exophthalmos)

    Anaphylaxis

    • A severe, life-threatening allergic reaction.
    • Triggered by exposure to an allergen.
    • Cascade of Events:
      • Exposure to allergen
      • Mast cell degranulation releasing histamine and other inflammatory mediators.
      • Vasodilation: Leads to a drop in blood pressure.
      • Bronchospasm: Causes difficulty in breathing.
      • Symptoms:
        • Hives
        • Swelling of the face, lips, and tongue
        • Difficulty breathing
        • Tightness in the chest
        • Low blood pressure and shock

    Humoral Immunity and Antibodies

    • Humoral immunity is a type of adaptive immunity mediated by antibodies produced by B-cells.
    • Key components of humoral immunity include: complement, B-cells, plasma cells, cytokines, chemokines, and antibodies.
    • Antibodies (AB) are proteins that bind to specific antigens (AG) and neutralize them.
    • AB can activate complement, promote opsonization, trigger inflammation, neutralize pathogens, and induce apoptosis.
    • B-cell Receptor (BCR) is an antibody attached to a B-cell.
    • Epitopes are segments on an antigen recognized by BCRs.

    B-Cell Development

    • B-Cell development occurs in the bone marrow.
    • Antigen-independent development includes:
      • Stage 1: Pro-B cell stage
      • Stage 2: Pre-B cell stage
      • Stage 3: Immature B cell stage (surface IgM)
      • Stage 4: Mature B cell stage (surface IgM and IgD)
    • Antigen-dependent development:
      • Stage 5: Activation by antigen
      • Stage 6: Proliferation and differentiation
    • Stages of mature B-cell development:
      • Stage 1: Naive B-cell
      • Stage 2: Activated B-cell (proliferation and differentiation)
      • Stage 3: Plasma cell (secretes large amounts of antibodies)
      • Stage 4: Memory B-cell (can rapidly respond to subsequent exposure to the same antigen)
      • Stage 5: Antibody-secreting cell
      • Stage 6: Antibody production

    Humoral Immunity

    • Primary immune response:
      • First exposure to the antigen
      • Slow response (takes several days to weeks)
      • Production of mostly IgM antibodies, followed by IgG and other isotypes
    • Secondary immune response:
      • Subsequent exposure to the same antigen
      • Rapid and robust response (within hours)
      • Production of mainly IgG antibodies
      • Memory B-cells are responsible for the rapid response

    Antibodies

    • Classes of antibodies:
      • IgG: Most abundant antibody in serum, can cross the placenta, activates complement
      • IgA: Found in mucosal secretions (e.g., saliva, tears, breast milk), protects against pathogens
      • IgM: First antibody produced during an immune response, activates complement
      • IgE: Involved in allergic reactions
      • IgD: Found on the surface of B-cells
    • Antibody structure:
      • Fab region (variable regions): Binds to specific antigens
      • Fc region (constant region): Binds to Fc receptors on other cells
      • Somatic hypermutation occurs in the variable region and improves antibody affinity over time.

    Passive Immunity

    • Naturally acquired:
      • IgG from mother to fetus through the placenta
      • IgA from mother to infant through breast milk
    • Artificially acquired:
      • Administration of pre-formed antibodies, like antivenom

    Active Immunity

    • Naturally acquired:
      • Infection by a pathogen (e.g., measles)
    • Artificially acquired:
      • Vaccination with weakened or inactivated pathogens

    Antibody Diversity

    • High number of antibodies produced by:
      • V(D)J recombination: Random rearrangement of variable, diversity, and joining gene segments during B-cell development
      • Somatic hypermutation: Introduction of random mutations in variable regions of antibody genes during antigen-dependent B-cell activation

    Functions of Antibodies

    • Neutralisation:
      • Covers viral surfaces, preventing binding to target cells.
      • Blocks bacterial toxins from binding to their target receptors.
    • Opsonization:
      • Antibodies bind to antigens, facilitating their phagocytosis by macrophages and neutrophils.
    • Complement activation:
      • Antibodies bind to pathogens, activating the complement cascade, which leads to pathogen lysis.
    • Antibody-dependent cell cytotoxicity (ADCC):
      • Antibodies bind to pathogens, facilitating their destruction by NK cells, macrophages, and neutrophils.
    • Mast cell degranulation:
      • Antibodies bind to mast cells, leading to their degranulation and the release of histamine, which causes allergic reactions.

    Antibody Isotype Switching

    • B-cells change their antibody isotype production based on cytokine signals from T-helper cells.
    • Different antibody isotypes are present at different stages of the immune response.
    • Antibody isotype indicates the stage and type of infection.

    Antibody Transport Across Mucosal Epithelium

    • IgA:
      • Transported from the bloodstream to mucosal surfaces such as the gut.
      • Protects against pathogens in mucosal tissues.

    Antibody-Dependent Cell Cytotoxicity (ADCC)

      1. Antibodies bind to antigens on the surface of target cells.
      1. NK cells or macrophages bind to the Fc region of the antibody.
      1. NK cells or macrophages release cytotoxic molecules that destroy the target cell.

    Antibodies in the Oral Cavity

    • Saliva: Contains IgA and other antibodies.
    • Gingival crevicular fluid (GCF): Contains IgG, IgA, and IgM.
    • Antibodies in the oral cavity:
      • Protect against dental caries and periodontal disease.
      • Help maintain oral health.

    Auto-Reactive B-Cell Disease - Graves' Disease

    • Graves' disease: An autoimmune disorder where antibodies are produced against the thyroid-stimulating hormone receptor.
    • Symptoms: Hyperthyroidism (e.g., increased heart rate, weight loss, anxiety, fatigue)

    Anaphylaxis - Type 1 Hypersensitivity

    • Anaphylaxis: A severe allergic reaction that can be life-threatening.
    • Steps involved:
      1. Initial exposure to allergen triggers sensitization.
      2. Antibodies (IgE) bind to mast cells.
      3. Subsequent exposure to the same allergen causes degranulation of mast cells, leading to histamine release.
      4. Histamine causes:
        • a. Vasodilation
        • b. Bronchospasm
        • c. Increased vascular permeability.

    Antibody Structure and Function

    • Antibodies are proteins that help the immune system to fight off infection.
    • There are five major types of antibodies: IgG, IgA, IgM, IgE, and IgD
    • There’s an acronym called “GAMED” to remember all antibody types.

    IgG Antibodies

    • IgG is the most abundant antibody in the blood plasma (65%-70%)
    • IgG is produced by plasma cells.
    • IgG is a monomer, meaning it exists as a single unit.
    • IgG is produced in both the primary and secondary immune responses.
    • IgG is more abundant in the secondary immune response.
    • IgG can activate the complement system.
    • IgG can bind to and neutralize viruses and other microbes.
    • IgG can precipitate antigens, which enhances opsonization and phagocytosis.
    • IgG can cross the placenta and confer passive immunity to the baby.

    IgA Antibodies

    • IgA is secreted by plasma cells.
    • IgA is a dimer, meaning it consists of two units linked together.
    • IgA is found in various body fluids, including saliva, sweat, mucus, milk, and the urogenital tract.
    • IgA protects against microbes in these fluids by binding to their antigens and neutralizing them.

    IgM Antibodies

    • IgM is secreted by plasma cells.
    • IgM can exist as a pentamer (five units linked together) or a monomer.
    • IgM is the first antibody produced during a primary immune response.
    • IgM can activate the complement system.
    • IgM can agglutinate (clump) red blood cells, which can cause a type II hypersensitivity reaction.

    IgE Antibodies

    • IgE is secreted by plasma cells.
    • IgE is a monomer.
    • IgE is found on mucosal surfaces, in the respiratory tract, and in some urogenital structures.
    • IgE binds to mast cells.
    • When IgE binds to an allergen, it triggers the release of inflammatory chemicals such as histamine, leukotrienes, and prostaglandins.
    • This can cause allergic reactions, including anaphylaxis.

    Allergic Reactions and Anaphylaxis

    • Increased capillary permeability in the respiratory tract leads to edema, causing swelling and airway restriction.
    • Allergens bind to smooth muscle cells in the bronchi, causing contraction and airway narrowing.
    • This contraction of smooth muscle cells in the bronchi is known as anaphylaxis, a type 1 hypersensitivity.

    The Role of IgE Antibodies

    • IgE antibodies are produced against parasitic worms.
    • Eosinophils, attracted by IgE antibodies, release major basic protein and cationic peptide, destroying the parasite.
    • IgE antibodies are found in small traces in blood plasma.

    IgD Antibodies and B Cell Receptors

    • IgD antibodies are monomeric and produced by plasma cells.
    • IgD antibodies are expressed on the B cell surface, acting as a B cell receptor.

    Somatic Hypermutation

    • Somatic hypermutation refers to the change in antibody production from IgM to IgG during the immune response.
    • The primary immune response involves initial production of IgM antibodies, followed by IgG antibody production.
    • Secondary exposure to an antigen leads to a rapid and robust production of IgG antibodies, highlighting the effect of somatic hypermutation.

    Passive vs. Active Immunity

    • Passive immunity is acquired without actively producing antibodies.
    • Naturally acquired passive immunity occurs through the transfer of antibodies from mother to child via placenta (IgG) and breast milk (IgA).
    • Artificially acquired passive immunity involves the administration of antibodies, such as anti-venom, to combat specific pathogens.
    • Active immunity involves the body's own production of antibodies against pathogens.
    • Naturally acquired active immunity occurs when the body is infected with a pathogen and produces antibodies in response.
    • Artificially acquired active immunity occurs through vaccination with weak or dead antigens, triggering antibody production.

    Antibody Structure

    • Antibodies consist of two heavy chains and two light chains.
    • The constant regions of heavy and light chains are responsible for complement protein binding.
    • The variable regions of heavy and light chains are unique for each antibody, allowing for specific antigen binding.
    • Each antibody molecule has two antigen binding sites.
    • IgM antibodies have 10 antigen binding sites due to their pentameric structure.

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    Humoral Immunity and Antibodies (2.2) PDF

    Description

    Explore the concepts of humoral immunity and the development of B cells in this engaging quiz. Understand the role of antibodies, B cells, and key components like the complement system and cytokines. Test your knowledge on how these elements contribute to the immune response.

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