Immunology: The Body's Defense System
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Questions and Answers

What is the primary function of the body's immune system?

  • To facilitate the growth of beneficial bacteria.
  • To eliminate non-pathogenic microorganisms from the body.
  • To provide defense reactions against pathogenic microorganisms. (correct)
  • To prevent all diseases from occurring.

    • Which term describes the first line of defense in the immune system?

  • Innate resistance. (correct)
  • Acquired immunity.
  • Specific immunity.
  • Adaptive resistance.

    • What is a key characteristic of innate (nonspecific) immunity?

  • It provides protection against any pathogen. (correct)
  • It has a memory component.
  • It is slow to respond.
  • It only responds to bacteria.

    • What discovery did Bruce Alan Beutler and Jules A. Hoffmann make regarding the immune system?

    <p>They identified Toll-like receptors and their role in innate immunity.</p> Signup and view all the answers

    Which statement about specific (acquired) immunity is correct?

    <p>It develops in response to specific microbes.</p> Signup and view all the answers

    What are the specialized immune cells involved in specific immunity?

    <p>B and T lymphocytes.</p> Signup and view all the answers

    How does innate immunity respond to pathogens?

    <p>It provides immediate, nonspecific response.</p> Signup and view all the answers

    What aspect distinguishes specific immunity from innate immunity?

    <p>Specific immunity requires prior exposure to an antigen.</p> Signup and view all the answers

    Which component of innate immunity serves as the first line of defense?

    <p>Intact skin</p> Signup and view all the answers

    What role do mucous membranes play in the immune system?

    <p>They line tracts and inhibit the entrance of microorganisms</p> Signup and view all the answers

    What is a characteristic of the epidermis of the skin?

    <p>It contains keratin, which is a protective protein</p> Signup and view all the answers

    Which of the following cells is considered a phagocyte in the innate immune response?

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

    What is the purpose of the lachrymal apparatus in the immune response?

    <p>To produce tears which wash away irritants</p> Signup and view all the answers

    What is a key function of normal microbiota in immune defense?

    <p>They occupy space and reduce pathogen colonization</p> Signup and view all the answers

    Which type of factors primarily constitute the first line of defense in innate immunity?

    <p>Physical and chemical factors</p> Signup and view all the answers

    Which immune response is characterized as the third line of defense?

    <p>Specialized lymphocytes such as T cells and B cells</p> Signup and view all the answers

    What role do normal microbiota play in the vagina concerning Candida albicans?

    <p>They compete with Candida albicans for nutrients.</p> Signup and view all the answers

    What is NOT included in the second line of defense against pathogens?

    <p>Skin barrier</p> Signup and view all the answers

    Which type of leucocyte is primarily responsible for antibody production?

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

    Which type of granulocyte is primarily active in the initial phases of an infection?

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

    What does the term 'phagocytosis' literally mean?

    <p>To devour particles</p> Signup and view all the answers

    Natural killer (NK) cells are primarily responsible for targeting which type of cells?

    <p>Infected body cells and tumor cells</p> Signup and view all the answers

    Monocytes differentiate into which of the following once they leave the bloodstream?

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

    How are dendritic cells primarily characterized in their immunological role?

    <p>They present antigens to T cells.</p> Signup and view all the answers

    What is the first phase of phagocytosis?

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

    Which substance is primarily involved in facilitating adherence during phagocytosis?

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

    What occurs during the ingestion phase of phagocytosis?

    <p>Phagocytes engulf microbes using pseudopodes.</p> Signup and view all the answers

    Which type of microorganisms can inhibit phagocytosis by preventing adherence?

    <p>Streptococcus pyogenes</p> Signup and view all the answers

    What do lysosomes release to aid in the digestion of pathogens?

    <p>Toxic oxygen products</p> Signup and view all the answers

    What is the pH level inside the phagosome during the ingestion phase of phagocytosis?

    <p>Acidic (pH 4)</p> Signup and view all the answers

    How can some microorganisms remain dormant within phagocytes?

    <p>By inhibiting the fusion of phagosomes and lysosomes</p> Signup and view all the answers

    What is the function of opsonization in phagocytosis?

    <p>To enhance the visibility of the pathogens to phagocytes</p> Signup and view all the answers

    What is the main function of phagocytes during inflammation?

    <p>To engulf and kill microorganisms</p> Signup and view all the answers

    What initiates tissue repair after injury?

    <p>The active phase of inflammation</p> Signup and view all the answers

    How does fever contribute to the defense against disease?

    <p>By enhancing the production of T lymphocytes</p> Signup and view all the answers

    What role does IL-1 play in the fever response?

    <p>It stimulates the release of prostaglandins</p> Signup and view all the answers

    What happens if body temperature rises above 44 to 46°C?

    <p>It can result in death</p> Signup and view all the answers

    Which of the following statements is true regarding the complement system?

    <p>It includes proteins that are important for antimicrobial activity</p> Signup and view all the answers

    Which physiological response occurs as fever progresses?

    <p>Constricted blood vessels and shivering</p> Signup and view all the answers

    What is a key characteristic of skin compared to cardiac muscle tissue during repair?

    <p>Skin has a high capacity for regeneration</p> Signup and view all the answers

    Study Notes

    Immunology: The Body's Defense System

    • Immunology is the science of the body's defense mechanisms against disease.
    • The term "immunity" comes from the latin word "immunis" meaning "free of burden."

    Immune Defenses

    • Innate immunity (nonspecific) is the first line of defense against infectious agents.
      • It is nonspecific, meaning it protects against any pathogen, regardless of its type.
      • It has no memory, meaning it can't recall previous encounters with foreign antigens.
    • Adaptive immunity (specific) is the third line of defense.
      • It is acquired during life and is based on a specific response to a specific microbe.
      • It has long-term memory for specific antigens.
      • It relies on specialized immune lymphocytes (B and T cells) and specific proteins (antibodies).

    Innate Immunity

    • First line of defense:
      • Physical barriers: intact skin, mucous membranes, mucus, tears, saliva, hairs, cilia, urine, vomiting, and defecation.
      • Chemical barriers: sebum, perspiration, lysozyme, gastric juice.
    • Second line of defense:
      • Phagocytes: neutrophils, eosinophils, dendritic cells, and macrophages.
      • Inflammation: a localized response to injury or infection triggered by chemical signals.
      • Fever: an increase in body temperature triggered by the release of the cytokine IL-1.
      • Antimicrobial substances: proteins including those of the complement system and interferons.

    Physical Barriers of the First Line of Defense

    • Skin: a strong physical barrier, with the outer layer composed of dead cells containing keratin.
    • Mucous Membranes: line the gastrointestinal, respiratory, and genitourinary tracts, offering less protection than the skin.
    • Mucus: a glycoprotein produced by goblet cells that traps microbes.
    • Tears: produced by the lachrymal apparatus of the eye, dilute and wash away microorganisms.
    • Normal microbiota: the bacteria that normally reside in the vagina and other body sites, alter pH conditions, preventing pathogen overgrowth.

    Second Line of Defense: Phagocytosis

    • Phagocytosis: the process of cellular engulfment of solid particles, a major mechanism of immune defense.
    • Phases of phagocytosis: chemotaxis, adherence, ingestion, and digestion.
    • Chemotaxis: the attraction of phagocytes to microbes, driven by chemical signals like microbial products, components of white blood cells, and complement fragments.
    • Adherence: the attachment of the phagocyte's membrane to the surface of the microbe.
    • Ingestion: the engulfment of the microbe by phagocytic cell extensions, creating a phagosome.
    • Digestion: lysosomes containing digestive enzymes fuse with the phagosome, forming a phagolysosome that destroys the microbe.
      • Lysosomal bactericidal factors include: hydrolyzing enzymes like lysozyme, lipase, protease, and toxic oxygen products.

    Microbial Evasion of Phagocytosis

    • Some microbes have evolved strategies to evade phagocytosis:
      • Inhibiting adherence: M protein (Streptococcus pyogenes), capsule (Streptococcus pneumoniae, Haemophilus influenzae).
      • Killing the phagocyte: leukocidin (Staphylococcus aureus), streptolysin (Streptococcus pyogenes).
      • Lysis of phagocyte membrane: membrane attack complex by Trypanosoma cruzi.
      • Inhibition of phagosome-lysosome fusion: Mycobacterium tuberculosis, Leishmania, Chlamydia, and HIV.
      • Remaining dormant inside the phagocyte: Brucella.
      • Formation of biofilms: preventing phagocytes from detaching bacteria from the biofilm structure.

    Inflammation

    • Inflammation is a localized response to injury or infection characterized by redness, swelling, heat, pain, and loss of function.
    • Key features: vasodilation (increased blood flow), increased permeability of blood vessels (allowing fluid and immune cells to enter the tissue), and migration of phagocytes to the site of injury.

    Fever

    • Fever: an abnormally high body temperature controlled by the hypothalamus.
    • Causes: infection triggers release of IL-1, which causes the hypothalamus to release prostaglandins, resetting the thermostat at a higher temperature.
    • Effects on body: constriction of blood vessels, increased metabolic rate, shivering, and vasodilation and sweating (as fever subsides).
    • Potential benefits: enhanced T lymphocyte production, intensified interferon action, slower growth of some microbes, and accelerated tissue repair.
    • Dangers: death if body temperature surpasses 44-46°C.

    Antimicrobial Substances

    • Complement System: a group of proteins that circulate in the blood, involved in the lysis of microbes, inflammation, and phagocytosis.
    • Interferons (IFNs): antiviral proteins that interfere with viral replication.

    Adaptive Immunity

    • Adaptive immunity: acquired during life, provides a more specific, targeted defense against specific pathogens.
    • Components: specialized lymphocytes, B cells and T cells, and antibodies.
    • B cells: responsible for antibody production.
    • T cells: responsible for cell-mediated immunity.
    • Antibodies: proteins that bind to specific antigens on pathogens, marking them for destruction.

    Key Figures

    • Bruce Beutler: American immunologist and geneticist, received the 2011 Nobel Prize in Physiology or Medicine for discovering Toll-like receptors (TLRs).
    • Jules Hoffmann: French biologist, shared the 2011 Nobel Prize with Beutler for their discoveries concerning the activation of innate immunity.
    • Ralf Steinman: Canadian immunologist, also received the 2011 Nobel Prize for his discovery of dendritic cells and their role in adaptive immunity.

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    Immunology Lecture Notes PDF

    Description

    Explore the essential concepts of immunology, focusing on the body's defense mechanisms against disease. This quiz covers innate and adaptive immunity, including their characteristics and functions in protecting against pathogens. Test your knowledge on the physical barriers and immune responses that play critical roles in maintaining health.

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