Immunology: Antigens and Immunogenicity
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What defines an antigen in the context of the immune system?

  • A protein that is exclusively recognized by T-cells
  • A molecule that can induce any form of immune response
  • Any molecule that can be processed into peptides
  • A molecule that can interact specifically with immunoglobulin or T-cell receptor complexed with MHC (correct)

    • Which statement best describes the relationship between immunogens and antigens?

  • Antigens can never be immunogens if they are recognized by macrophages.
  • Immunogens are stronger than antigens and always induce a response.
  • All immunogens are antigens, but not all antigens are immunogens. (correct)
  • Immunogens are a type of antigen found only in bacteria.

    • Which type of immunogen demonstrates the highest immunogenicity?

  • Polysaccharides
  • Proteins (correct)
  • Nucleic Acids
  • Lipids

    • What property of an immunogen refers to its recognition as non-self by the immune system?

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

    Which of the following immunogenicity factors primarily influences the ability of a molecule to induce an immune response?

    <p>The phylogenetic distance between the source species</p> Signup and view all the answers

    What was the primary method used by the Chinese in the 12th century to immunize against smallpox?

    <p>Inhaling ground crusts from smallpox pustules</p> Signup and view all the answers

    Which scientist is known for developing the first rabies vaccine?

    <p>Louis Pasteur</p> Signup and view all the answers

    What is a key goal of science communication?

    <p>To ensure the audience comprehends the message</p> Signup and view all the answers

    Which of the following statements reflects a principle of integrity in science communication?

    <p>Being transparent and avoiding misleading data</p> Signup and view all the answers

    What was one of the significant contributions of Edward Jenner in vaccine development?

    <p>Publishing findings on smallpox vaccination</p> Signup and view all the answers

    What was a method used by the Turks for smallpox inoculation?

    <p>Inserting crusts into cuts in the skin</p> Signup and view all the answers

    What is an essential consideration when disseminating scientific findings to the public?

    <p>Presenting both facts and hypotheses clearly</p> Signup and view all the answers

    What significant aspect of society influences how people make daily decisions regarding information?

    <p>Social media's rapid dissemination of information</p> Signup and view all the answers

    What is a significant advantage of certain vaccines mentioned?

    <p>They are stable and easier to distribute.</p> Signup and view all the answers

    Which method is NOT used for preparing subunit vaccines?

    <p>Attenuating the pathogen.</p> Signup and view all the answers

    What is a major characteristic of toxoid vaccines?

    <p>They are produced by altering bacterial toxins.</p> Signup and view all the answers

    What is a challenge associated with subunit vaccines?

    <p>They require multiple doses for adequate immunity.</p> Signup and view all the answers

    What is the primary role of the Recombinational Signal Sequences (RSS)?

    <p>To guide RAG in the orientation for gene rearrangement</p> Signup and view all the answers

    What is one feature of engineered vaccines?

    <p>They engage innate immune receptors.</p> Signup and view all the answers

    Which type of vaccine is best suited to elicit a strong CTL response?

    <p>Engineered vaccines.</p> Signup and view all the answers

    What does the 12/23 rule refer to in chromosome rearrangement?

    <p>It indicates that rearrangement occurs between RSS with specific spacer lengths.</p> Signup and view all the answers

    What is the result of allelic exclusion in B-cell development?

    <p>Only one allele of a gene rearranges at a time.</p> Signup and view all the answers

    Why might subunit vaccines struggle with pathogens that are antigenically diverse?

    <p>They can only accommodate specific antigens.</p> Signup and view all the answers

    What is an example of a method to prepare subunit vaccines?

    <p>Recombinant DNA technology.</p> Signup and view all the answers

    What usually initiates the inhibition of further allele rearrangement in B-cells?

    <p>Successful rearrangement of one allele</p> Signup and view all the answers

    What is the significance of constant regions in antibodies?

    <p>They are involved in the effector functions of the antibodies.</p> Signup and view all the answers

    Which immunoglobulin is typically produced first by a B-cell?

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

    What mechanism allows an antibody to switch its isotype from IgM to IgG?

    <p>Physical translocation and cutting of DNA at switch regions</p> Signup and view all the answers

    What often prevents patients from producing different isotypes of antibodies?

    <p>Mutation in the AID enzyme</p> Signup and view all the answers

    Which part of the antibody structure is modified without affecting VDJ segments?

    <p>The constant region</p> Signup and view all the answers

    What is the role of switch regions in antibody class switching?

    <p>To guide the cutting and joining of DNA for isotype changes</p> Signup and view all the answers

    What role does IL-1 play in the activation of T-helper cells?

    <p>It enhances the activation of T-helper cells.</p> Signup and view all the answers

    Which of the following describes the function of adjuvants like alum and Freund's complete?

    <p>They prolong antigen exposure in the immune system.</p> Signup and view all the answers

    What is an epitope?

    <p>A small site on a macromolecule recognized by lymphocytes.</p> Signup and view all the answers

    Which statement regarding B-cell epitopes is correct?

    <p>Epitopes must be hydrophilic and accessible on the antigen's surface.</p> Signup and view all the answers

    Which characteristic is true about T-cell epitopes?

    <p>T-cells only recognize processed protein fragments presented by MHC.</p> Signup and view all the answers

    What defines the affinity of an antibody for an antigen?

    <p>The strength of non-covalent interactions between Ab and Ag.</p> Signup and view all the answers

    What is the difference between avidity and affinity?

    <p>Avidity indicates how well an antibody binds to one antigen, while affinity measures overall bond strength in multivalent scenarios.</p> Signup and view all the answers

    Which type of bond is NOT involved in antigen-antibody interactions?

    <p>Covalent bonds</p> Signup and view all the answers

    What is the role of costimulatory signals in T-cell activation?

    <p>They are necessary for T-cells to respond to an antigen.</p> Signup and view all the answers

    What types of antigens can B-cells recognize?

    <p>Both soluble and insoluble antigens as long as epitopes are accessible.</p> Signup and view all the answers

    What impacts the immunodominance of T-cell epitopes?

    <p>The MHC molecules expressed and the TCR repertoire of the individual.</p> Signup and view all the answers

    What is the significance of the hydrophobic and hydrophilic regions of T-cell epitopes?

    <p>Hydrophobic regions bind to MHC, while hydrophilic regions bind to TCR.</p> Signup and view all the answers

    What happens when T-helper cells are stimulated by antigens without a second costimulatory signal?

    <p>They will respond weakly or not at all.</p> Signup and view all the answers

    What is the principal difference between how B-cells and T-cells recognize antigens?

    <p>B-cells bind directly to antigens, whereas T-cells recognize processed antigens presented by MHC.</p> Signup and view all the answers

    Study Notes

    Antigens

    • The immune system identifies foreign and self molecules as good or bad based on context.
    • Antigens specifically interact with immunoglobulins (Ig) receptors on B-cells or T-cell receptors complexed with MHC.
    • Immunogens are a subset of antigens that induce a specific immune response.

    Immunogenicity

    • Humoral immunogens stimulate B-cells and are mostly proteins.
    • Cell-mediated immunogens stimulate T-cells and mainly consist of proteins, some lipids, and glycolipids.
    • Four properties contribute to immunogenicity:
      • Foreignness: The greater the phylogenetic distance between the antigen and the host, the greater the immunogenicity.
      • Prolonged Exposure: Adjuvants like alum and Freund's adjuvant bind and precipitate antigens, prolonging exposure and enhancing immune response.
      • Co-stimulatory Signal: Adjuvants like LPS and Freund's adjuvant upregulate co-stimulatory signals, activating T-cells and amplifying the immune response.
      • Size and Complexity: Larger, more complex antigens are more likely to be immunogenic.

    Epitopes

    • Lymphocytes recognize specific sites on antigens called epitopes or antigenic determinants.
    • B-cell epitopes must be accessible on the surface of native molecules, typically composed of 6-7 amino acids or sugars.
    • T-cell epitopes are recognized only after antigen processing, presented within MHC molecules, and typically consist of peptides 7-20 amino acids long.

    Antigen-Antibody Interactions

    • Antigen-antibody interactions involve specific, reversible binding, driven by multiple non-covalent bonds.
    • Affinity refers to the strength of interaction between a single antibody binding site and a single epitope.
    • Avidity refers to the overall strength of multiple interactions between a multivalent antibody and antigen.

    Antibody Isotypes

    • Antibodies can undergo class switching, changing their isotype (e.g. IgM to IgG) without altering their variable regions.
    • Class switching involves DNA rearrangement at the constant region of the antibody gene.
    • The constant region determines the antibody's effector functions.

    Vaccines

    • Vaccines, derived from the Latin word for "cow" (vacca), were first used in the 12th century using smallpox pustules.
    • Edward Jenner developed the first smallpox vaccine in 1798 using cowpox material.
    • Louis Pasteur developed the first attenuated vaccines for cholera, anthrax, and rabies.
    • Modern vaccines can be:
      • Inactivated (killed) vaccines: Contain killed pathogens or inactive toxins. Provide weaker and shorter-lived immunity than other types.
      • Subunit vaccines: Contain specific antigens or toxins. Can be produced through chemical extraction, recombinant DNA technology, or chemical synthesis.
      • Toxoid vaccines: Chemically modified bacterial toxins that are no longer toxic but still stimulate an immune response.
      • Engineered vaccines: "Trojan horse" approach using attenuated pathogens or other vectors (viruses/bacteria) to deliver antigens.
      • DNA/RNA vaccines: Introduce genetic material encoding antigens into the host.

    Vaccine Development

    • New vaccine development seeks to create safe and effective vaccines that trigger a robust immune response.
    • Strategies include:
      • Designing vaccines that target conserved antigens.
      • Enhancing antigen presentation by incorporating adjuvant components.
      • Developing vaccines that elicit both antibody and T-cell responses.
    • Vaccine development often focuses on addressing specific challenges like:
      • Antigenic diversity and variability of pathogens: Creating vaccines effective against multiple strains.
      • Safety concerns: Minimizing risks like allergic reactions or infection.

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    Description

    Explore the key concepts of antigens and immunogenicity in the immune system. This quiz covers the interaction between antigens and immune cells, the properties affecting immunogenicity, and how B-cells and T-cells respond to pathogens. Test your understanding of these fundamental principles in immunology.

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