5.1 Antigens
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Questions and Answers

What is the function of the carrier group in an immunogenic substance?

  • Confer the size (correct)
  • Provide specificity
  • Activate immune cells
  • Enhance antigen-antibody binding
  • Which component of an antigen molecule is responsible for specificity?

  • Conferring size
  • Carrier
  • Macromolecular protein
  • Determinants (epitopes) (correct)
  • How does the difference in structure between a foreign antigen and an animal's own antigen affect the immune response intensity?

  • It increases the immune response (correct)
  • It reduces the immune response
  • It has no impact on the immune response
  • It weakens the immune response
  • What are determinants or epitopes of an antigen?

    <p>Distinct molecular features (C)</p> Signup and view all the answers

    Which cell type specifically binds to determinants or epitopes of an antigen?

    <p>T cells (A)</p> Signup and view all the answers

    What type of antigens can directly stimulate B cells to produce antibodies without the need for T cell help?

    <p>T-independent antigens (C)</p> Signup and view all the answers

    What is a characteristic feature of T-independent antigens?

    <p>Polymeric structure (D)</p> Signup and view all the answers

    Why do T-independent antigens persist for longer periods and continue stimulating the immune system?

    <p>They are resistant to degradation (B)</p> Signup and view all the answers

    Which property is associated with T-independent antigens that can activate B cell clones specific for other antigens?

    <p>Polyclonal activation (A)</p> Signup and view all the answers

    What do polysaccharides generally represent in terms of antigenic classification?

    <p>T-independent antigens (B)</p> Signup and view all the answers

    What distinguishes T-independent antigens from other types of antigens in terms of their immune responses?

    <p>Polymeric structure (C)</p> Signup and view all the answers

    What is the part of an antibody that recognizes the epitope called?

    <p>Paratope (D)</p> Signup and view all the answers

    Which type of antigen lacks immunogenicity unless attached to a large carrier molecule?

    <p>Haptens (D)</p> Signup and view all the answers

    What property do haptens have but lack immunogenicity unless attached to a large carrier?

    <p>Antigenicity (B)</p> Signup and view all the answers

    Which type of antigens are represented by various natural constituents seen in animals, plants, and microorganisms?

    <p>Natural antigens (C)</p> Signup and view all the answers

    Complete antigens have both colloidal support (carrier) and __________.

    <p>Epitopes (A)</p> Signup and view all the answers

    In the context of antigens, what are substances that are non-immunogenic but can react with the products of a specific immune response known as?

    <p>Haptens (A)</p> Signup and view all the answers

    What is the chemical nature of capsular antigens in most encapsulated bacteria?

    <p>Polysaccharidic (C)</p> Signup and view all the answers

    What is the role of anticapsular antibodies in an infected animal?

    <p>They enhance phagocytosis and intracellular destruction (A)</p> Signup and view all the answers

    What is the structure of a virus?

    <p>Nucleic acid core surrounded by a protein layer and an envelope containing lipoproteins and glycoproteins (A)</p> Signup and view all the answers

    What is the source of endogenous antigens?

    <p>Cytoplasmic membrane of mammalian cells (A)</p> Signup and view all the answers

    What is the role of the capsule in bacteria?

    <p>It protects against phagocytosis and intracellular destruction (A)</p> Signup and view all the answers

    What is the role of foreign molecules in food?

    <p>They can trigger an immune response and cause an allergic reaction (A)</p> Signup and view all the answers

    What type of antigens are characterized by a few copies of many different antigenic determinants?

    <p>T-dependent antigens (C)</p> Signup and view all the answers

    Which component of the Gram-negative bacterial cell wall is responsible for most of its antigenicity?

    <p>Lipopolysaccharide (LPS) (B)</p> Signup and view all the answers

    What is the primary chemical nature of flagellar antigens (H antigens) extracted from bacterial flagella?

    <p>Protein (A)</p> Signup and view all the answers

    How do fimbrial antigens (F antigens) help some Gram-negative bacteria?

    <p>By facilitating attachment to cell surfaces (A)</p> Signup and view all the answers

    Which component of the Gram-positive bacterial cell wall is involved in the transport of ions across the cell wall?

    <p>Lipoteichoic acids (A)</p> Signup and view all the answers

    What is the role of pili (sex pili) in bacteria?

    <p>Mating and movement (D)</p> Signup and view all the answers

    What is the general immunogenicity of proteins?

    <p>They are usually very good immunogens (B)</p> Signup and view all the answers

    Which type of antigen is usually poorly immunogenic?

    <p>Nucleic acids (A)</p> Signup and view all the answers

    What makes antigens more easily phagocytosed and generally more immunogenic?

    <p>Degradability (B)</p> Signup and view all the answers

    Why are lipids generally considered non-immunogenic?

    <p>They lack degradability (D)</p> Signup and view all the answers

    Which of the following is a characteristic of good immunogens?

    <p>Dependence on the degree of foreignness (A)</p> Signup and view all the answers

    What distinguishes polysaccharides as good immunogens?

    <p>Having a high degree of degradability (D)</p> Signup and view all the answers

    What is the role of the determinants (epitopes) in an immunogenic substance?

    <p>Providing specificity by being bound by antibodies, B cells, or T cells (C)</p> Signup and view all the answers

    What does the carrier group in an immunogenic substance primarily contribute to?

    <p>Size and detectability of the molecule (D)</p> Signup and view all the answers

    What is the main function of the carrier in an immunogenic substance?

    <p>Making the molecule detectable by the immune cells (D)</p> Signup and view all the answers

    Which molecules' distinct surface features are capable of being bound specifically by antibodies, B cells, or T cells?

    <p>Determinants (epitopes) (C)</p> Signup and view all the answers

    In an immunogenic substance, what contributes more to the intensity of the immune response?

    <p>Difference in structure between foreign antigens and animal's own antigens (A)</p> Signup and view all the answers

    How do capsules protect bacteria?

    <p>By overcoming the effects of the capsule (C)</p> Signup and view all the answers

    What is the primary chemical nature of bacterial capsular antigens?

    <p>Polysaccharidic (D)</p> Signup and view all the answers

    What is the role of endogenous antigens presented by MHC I?

    <p>Signal to cytotoxic T cells (D)</p> Signup and view all the answers

    What triggers an immune response to foreign molecules in food?

    <p>Generating allergic reactions (A)</p> Signup and view all the answers

    Which type of antigens are represented by the mosaic of protein molecules on mammalian cell membranes?

    <p>Nonmicrobial antigens (C)</p> Signup and view all the answers

    Why are viruses considered obligate intracellular parasites?

    <p>As they require a living host cell for replication (B)</p> Signup and view all the answers

    What is a defining property of T-independent antigens?

    <p>Polymeric structure with repeated antigenic determinants (B)</p> Signup and view all the answers

    How do T-independent antigens differ from other antigens in terms of B cell activation?

    <p>T-independent antigens activate B cell clones specific for other antigens (A)</p> Signup and view all the answers

    Which cells are directly stimulated by T-independent antigens for antibody production?

    <p>B cells (A)</p> Signup and view all the answers

    What type of immune response do T-independent antigens generally evoke?

    <p>Humoral response (B)</p> Signup and view all the answers

    Why do T-independent antigens persist for longer periods within the immune system?

    <p>They resist degradation and have repeated antigenic determinants (D)</p> Signup and view all the answers

    Which feature distinguishes T-independent antigens from T-dependent antigens?

    <p>Ability to activate B cells without T cell help (A)</p> Signup and view all the answers

    What type of response occurs when an animal mounts immune responses against normal body components?

    <p>Autoimmune responses (B)</p> Signup and view all the answers

    Which of the following types of antigens can activate a large fraction of T cells, inducing a cytokine storm?

    <p>Superantigens (D)</p> Signup and view all the answers

    What is the characteristic of superantigens when compared to conventional T-dependent antigens in terms of T cell activation?

    <p>Polyclonal activation of up to 25% of T cells (C)</p> Signup and view all the answers

    Which of the following is NOT an example of superantigens associated with certain conditions or microorganisms?

    <p>Influenza virus antigens (D)</p> Signup and view all the answers

    In superantigenic responses, what fraction of the T cell population can be activated by these antigens?

    <p>Up to 25% (C)</p> Signup and view all the answers

    What distinguishes superantigens from conventional T-dependent antigens in terms of the immune response they trigger?

    <p>Inducing a cytokine storm (A)</p> Signup and view all the answers

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