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Questions and Answers
What is the primary function of adjuvants in vaccines?
What is the primary function of adjuvants in vaccines?
Which antibody class is known for its ability to cross the placenta?
Which antibody class is known for its ability to cross the placenta?
What is the main characteristic of hypervariable regions in antibodies?
What is the main characteristic of hypervariable regions in antibodies?
Which immunoglobulin is primarily found in secretions such as tears and saliva?
Which immunoglobulin is primarily found in secretions such as tears and saliva?
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Which of the following statements about IgM is true?
Which of the following statements about IgM is true?
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What is the function of Antibody-Dependent Cell-Mediated Cytotoxicity (ADCC)?
What is the function of Antibody-Dependent Cell-Mediated Cytotoxicity (ADCC)?
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What role does IgE play in the immune system?
What role does IgE play in the immune system?
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Which of the following is NOT a function of antibodies?
Which of the following is NOT a function of antibodies?
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Freund's complete adjuvant is specifically used in which type of setting?
Freund's complete adjuvant is specifically used in which type of setting?
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Which of the following describes the structure of antibodies?
Which of the following describes the structure of antibodies?
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What is the primary factor that distinguishes immunogens from antigens?
What is the primary factor that distinguishes immunogens from antigens?
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Which molecular weight range is typically considered immunogenic?
Which molecular weight range is typically considered immunogenic?
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What characteristic do homopolymers of amino acids exhibit regarding immunogenicity?
What characteristic do homopolymers of amino acids exhibit regarding immunogenicity?
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How does the dosage of an immunogen affect the immune response?
How does the dosage of an immunogen affect the immune response?
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Which of the following statements about haptens is true?
Which of the following statements about haptens is true?
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Which class of antigens is associated with being very immunogenic?
Which class of antigens is associated with being very immunogenic?
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What does cross-reactivity refer to in the context of antibodies?
What does cross-reactivity refer to in the context of antibodies?
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What is the role of an adjuvant in immunology?
What is the role of an adjuvant in immunology?
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Which factor does NOT contribute to the immunogenicity of a substance?
Which factor does NOT contribute to the immunogenicity of a substance?
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Which statement about nucleic acids and immunogenicity is accurate?
Which statement about nucleic acids and immunogenicity is accurate?
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What is a unique characteristic of aluminum hydroxide as an adjuvant?
What is a unique characteristic of aluminum hydroxide as an adjuvant?
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Which of the following best describes the role of hypervariable regions in antibodies?
Which of the following best describes the role of hypervariable regions in antibodies?
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What is a primary function of IgA in the immune system?
What is a primary function of IgA in the immune system?
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Which IgG subclass is primarily known for opsonization?
Which IgG subclass is primarily known for opsonization?
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Which statement accurately differentiates immunogens from antigens?
Which statement accurately differentiates immunogens from antigens?
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What distinguishes the immunological response of IgM from other immunoglobulins?
What distinguishes the immunological response of IgM from other immunoglobulins?
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Which of the following immunoglobulin classes mediates Type I hypersensitivity reactions?
Which of the following immunoglobulin classes mediates Type I hypersensitivity reactions?
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What is the significance of molecular weight in determining immunogenicity?
What is the significance of molecular weight in determining immunogenicity?
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Which property must a substance possess to enhance its immunogenicity as an adjuvant?
Which property must a substance possess to enhance its immunogenicity as an adjuvant?
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Which of the following statements about antibody-dependent cell-mediated cytotoxicity (ADCC) is incorrect?
Which of the following statements about antibody-dependent cell-mediated cytotoxicity (ADCC) is incorrect?
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What defines haptens in relation to immunogenicity?
What defines haptens in relation to immunogenicity?
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Which immune function is NOT primarily associated with antibodies?
Which immune function is NOT primarily associated with antibodies?
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Which major class of antigens is typically associated with high immunogenicity?
Which major class of antigens is typically associated with high immunogenicity?
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What is one of the primary roles of adjuvants in vaccine formulations?
What is one of the primary roles of adjuvants in vaccine formulations?
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How does chemical complexity affect the immunogenicity of a substance?
How does chemical complexity affect the immunogenicity of a substance?
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Which comment about the distribution of antibody isotypes is FALSE?
Which comment about the distribution of antibody isotypes is FALSE?
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What is a key factor in antigen processing that influences immunogenicity?
What is a key factor in antigen processing that influences immunogenicity?
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What does cross-reactivity imply concerning antibodies?
What does cross-reactivity imply concerning antibodies?
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Which requirement is NOT necessary for a substance to be considered an immunogen?
Which requirement is NOT necessary for a substance to be considered an immunogen?
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What type of antigens are polysaccharides typically associated with?
What type of antigens are polysaccharides typically associated with?
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Study Notes
Immunogens and Antigens
- Immunogens induce an immune response; antigens bind to antibodies or T cells.
- All immunogens are antigens, but not all antigens are immunogens.
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Requirements for Immunogenicity:
- Foreignness: Substances not recognized as "self" (exceptions exist in autoimmune diseases). More foreign = more immunogenic.
- Size: Generally, molecules larger than 6 kDa are immunogenic; smaller than 1 kDa are typically not (e.g., penicillin, aspirin).
- Chemical Complexity: Homopolymers of amino acids are not immunogenic.
- Degradability: Susceptible to enzymatic degradation is important for antigen presentation.
- Dosage: Insufficient doses can cause tolerance; repeated administrations may be needed for an adequate immune response.
Hapten
- Low molecular weight (antigen but not immunogen).
- Non-immunogenic alone.
- Requires conjugation with an immunogenic compound (carrier) to become immunogenic.
Epitopes Recognized by Lymphocytes
- Surface antigens
- Peptides
Major Classes of Antigens
- Carbohydrates (polysaccharides): Immunogenic as part of glycoproteins.
- Lipids: Rarely immunogenic.
- Nucleic Acids: Not immunogenic, except in some diseases (e.g., systemic lupus erythematosus – SLE).
- Proteins, Glycoproteins: Highly immunogenic.
Cross-reactivity
- Ability of an antibody targeting one antigen to react with a second, related antigen.
- Often occurs with closely related antigens due to shared epitopes.
Adjuvant
- Enhances immunogenicity of an immunogen.
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Mechanism of action:
- Physically prolongs antigen persistence/slows release.
- Induces local inflammation and immune cell proliferation.
- Improves compound uptake and processing by immune cells.
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Examples:
- Humans: Aluminum hydroxide (or phosphate) – FDA-approved.
- Animals: Freund's complete adjuvant (oil-in-water emulsion with killed mycobacteria).
Function & Structure of Antibodies
- Antibodies: Globular proteins produced by plasma cells (B lymphocytes). Exist as secreted and membrane-bound forms, forming B cell receptors.
- Functions: Neutralize toxins/viruses, immobilize bacteria/parasites, activate complement, initiate opsonization, and mediate antibody-dependent cell-mediated cytotoxicity (ADCC).
Antibody Structure
- Antigen binding: Occurs through hypervariable regions.
- Fc: The fragment of an antibody that interacts with other molecules
Hypervariable Regions
- Highly variable amino acid sequences.
- Present in three locations in both light and heavy chains.
Five Major Classes of Antibodies
- Different classes with specific functions and distributions.
Distribution of Antibody Isotypes in Body Fluids and Secretions
- Different isotypes (IgM, IgG, IgA, IgE) have different roles and distributions in body fluids and secretions.
IgG
- Four subclasses (IgG1, IgG2, IgG3, IgG4).
- Crosses the placenta.
- Involved in opsonization, ADCC, complement activation, and toxin/viral neutralization.
IgM
- First antibody class produced during infection/immunization.
- Highly efficient in complement activation.
IgA
- Predominantly found in secretions (tears, saliva, mucus).
- Important first line defense in the respiratory and mucosal systems.
- Exhibits antibacterial and antiviral activity.
IgE
- Mediates Type I hypersensitivity reactions.
- Levels rise during parasitic infections.
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Description
This quiz explores the key concepts of immunogens and antigens, including their characteristics and requirements for immunogenicity. It also covers haptens and their role in eliciting immune responses. Perfect for students studying immunology and related fields.
