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What roles do antibodies play in the immune response?
What is the function of the Fab region of an antibody?
Which process describes the alteration of B-cell antibody isotype production in response to T-helper cell cytokines?
What is a key feature of the IgG antibody?
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Which statement about somatic hypermutation is true?
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What is the result of opsonization in the immune response?
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Which antibody is primarily involved in passive immunity through breast milk?
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Which immune response is characterized by the rapid production of antibodies after a secondary exposure to an antigen?
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Which statement correctly describes the role of antibodies in humoral immunity?
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What accurately describes the structure of antibodies?
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What is the primary mechanism through which antibodies neutralize toxins?
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Which statement most accurately describes passive immunity?
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What is implied by class switching in B-cells?
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Which mechanism directly mediates antibody-dependent cell cytotoxicity (ADCC)?
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What is a consequence of somatic hypermutation in B-cells?
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How do secretory IgA antibodies function in mucosal immunity?
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What percentage of IgG antibodies are found within blood plasma and extracellular fluids?
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What type of immunity do IgG antibodies provide to the baby from the mother?
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What form do secretory IgA antibodies take?
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Where can IgA antibodies be found in the body?
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What is the primary function of IgM antibodies?
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What type of structure characterizes IgM antibodies?
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What is the primary cell type responsible for secreting antibodies?
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What causes IgA antibodies to be effective in mucosal defenses?
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Which percentage of IgG antibodies is typically found in blood plasma?
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What type of structure do IgG antibodies have?
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What beneficial feature do IgA antibodies provide through breast milk?
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During which immune response are IgG antibodies produced in greater abundance?
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Which antibody type is most abundant during the secondary immune response?
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What mechanism allows IgG antibodies to enhance complement proteins?
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Which mechanism describes the process where antibodies bind free antigens to enhance phagocytosis?
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In which fluid types are IgA antibodies predominantly found?
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What happens when IgG antibodies bind to a virus particle?
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Which of the following processes do IgG antibodies NOT participate in?
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What is the role of IgG antibodies in relation to viruses?
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Which antibody is notably involved in defense against gastrointestinal bacteria?
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What is the term for the complex formed when complement proteins are activated by antibodies?
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What role do plasma cells play in antibody production?
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Which type of immunity is primarily provided by IgG antibodies from the placenta to a fetus?
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What is the likely consequence of a deficiency in IgG antibody production?
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What happens during opsonization in the context of IgG antibodies?
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Which characteristic of IgG antibodies enhances inflammation by interacting with complement proteins?
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How do IgG antibodies contribute to the immune response when encountering a new antigen?
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What is the function of the Fc epsilon r1 receptor on mast cells?
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What immediate effect does the binding of IgE antibodies to mast cells have?
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What occurs during an anaphylactic reaction related to airway constriction?
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What role do leukotrienes play in allergic reactions?
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What can result from increased capillary permeability in the respiratory mucosa?
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Which antibody is primarily involved in the immune response to parasitic infections?
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What is the primary consequence of histamine release from mast cells?
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How do eosinophils contribute to the immune response to parasites?
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What type of hypersensitivity reaction is primarily associated with anaphylaxis?
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What is the primary role of IgD antibodies in the immune response?
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What happens to airway size when smooth muscle cells in the bronchi contract?
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Why is persistent exposure to allergens potentially dangerous?
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What outcome is associated with the action of inflammatory mediators like prostaglandins during an allergic response?
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What is the function of disulfide bonds in the structure of antibodies?
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What distinguishes IgM antibodies from other classes of antibodies during an immune response?
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How do variable heavy and light chains contribute to antibody specificity?
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What is one major role of IgM antibodies concerning foreign antigens?
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What is the total number of antigen-binding sites present in an IgM antibody?
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Which of the following processes describes what happens when IgM antibodies bind to mismatched blood during transfusion?
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What feature distinguishes the variable regions of antibodies?
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What type of hypersensitivity is associated with mismatched blood transfusions involving IgM antibodies?
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Why is it significant that antibodies have two antigen-binding sites?
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Which characteristic is true for IgE antibodies?
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What role do variable regions specifically play in the immune response?
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Where are IgE antibodies primarily found within the body?
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In terms of antibody structure, what does the term 'constant region' refer to?
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How many antigen-binding sites does a pentameric IgM antibody possess?
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What characteristic of antibodies allows them to bind effectively to foreign invaders?
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Which condition could indicate that a person is undergoing a primary immune response based on antibody levels?
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What common function do both IgM and IgE antibodies share?
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What is the role of the complement system when activated by IgM antibodies?
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How does the structure of IgM antibodies contribute to their function?
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Which of the following best describes the physiological importance of IgM antibodies during an infection?
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Which antibody type is predominantly involved in allergic responses?
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What specific tissues or areas are IgE antibodies primarily associated with?
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What occurs first during the primary immune response to an antigen?
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What is indicated by the term 'somatic hypermutation' in the context of immune response?
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During the secondary immune response, which antibody is primarily produced?
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Which phase of the immune response is characterized by a delay before antibody production begins?
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What initiates the switch from producing IgM antibodies to IgG antibodies in B-cells?
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What happens to the levels of IgM during the secondary immune response?
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Which of the following best describes the timeline of antibody production after first exposure to an antigen?
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In the context of B-cell activation, what role do microbes play?
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What defines the relationship between IgM and IgG during the immune response?
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What characterizes the 'lag period' observed after antigen exposure?
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How does cytokine signaling influence the production of antibodies in B-cells?
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What is the function of the B-cell receptor in the immune response?
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What can happen to IgG levels during repeated antigen exposure?
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What distinguishes passive immunity from active immunity?
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Which example represents naturally acquired passive immunity?
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What is an example of artificially acquired active immunity?
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Why is the administration of antivenom considered a form of passive immunity?
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Which type of immunity is characterized by the production of antibodies as a direct response to infection?
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What role does somatic hypermutation play in antibody production?
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In terms of antibody structure, what is the function of the constant heavy chain?
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What is a common misconception about artificially acquired passive immunity?
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Which of the following correctly describes artificially acquired passive immunity?
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What is the major difference between naturally acquired and artificially acquired active immunity?
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What is the main misconception about antibodies derived from maternal sources?
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What mechanism enables vaccines to provide long-lasting protection?
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How does the structure of antibodies contribute to their function?
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What is the relationship between somatic hypermutation and the production of IgG antibodies during secondary responses?
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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
- Antigen-independent stage:
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)
-
- Antibodies bind to antigens on the surface of target cells.
-
- NK cells or macrophages bind to the Fc region of the antibody.
-
- 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:
- Initial exposure to allergen triggers sensitization.
- Antibodies (IgE) bind to mast cells.
- Subsequent exposure to the same allergen causes degranulation of mast cells, leading to histamine release.
- 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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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.
