Immunology Chapter on Innate Defenses
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Questions and Answers

Which of the following are considered innate defenses? (Select all that apply)

  • Antibodies
  • T cells
  • Phagocytes (correct)
  • Inflammation (correct)
  • Skin (correct)

    • The immune system is a system of organs, rather than a functional system.

    False

    What are the main types of antimicrobial proteins? (Select all that apply)

  • Interferons (correct)
  • Complement (correct)
  • Prostaglandins
  • Cytokines
  • Histamine

    • What is the main function of MHC proteins? (Use complete sentences)

    <p>MHC proteins are essential for presenting antigens to T lymphocytes, which are a crucial part of the adaptive immune system. By displaying fragments of antigens on their surface, MHC proteins help T cells recognize and target specific pathogens.</p> Signup and view all the answers

    Which type of immunity is characterized by the production of antibodies?

    <p>Humoral immunity</p> Signup and view all the answers

    Memory cells are a type of effector cell that is involved in fighting off infections.

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

    Which of these is NOT a benefit of inflammation?

    <p>Triggers autoimmune responses</p> Signup and view all the answers

    The process of ______ refers to the engulfing and destruction of particulate matter and pathogens by specialized immune cells.

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

    What are the four cardinal signs of inflammation?

    <p>The four cardinal signs of inflammation are redness, heat, swelling, and pain.</p> Signup and view all the answers

    Natural killer cells are the main cells responsible for the adaptive immune response.

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

    Match the following events in the inflammatory response with their descriptions:

    <p>Leukocytosis = Increased number of white blood cells in circulation Margination = Neutrophils adhere to the walls of blood vessels Diapedesis = Neutrophils squeeze through the walls of blood vessels Chemotaxis = Neutrophils are drawn to the site of infection by chemical signals</p> Signup and view all the answers

    The immune system is considered a functional system rather than an organ system.

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

    What are the two branches of the immune system?

    <p>Innate and adaptive immune responses</p> Signup and view all the answers

    Which of the following is NOT a surface barrier included in the first line of defense?

    <p>Lymphatic system</p> Signup and view all the answers

    What are the four cardinal signs of inflammation?

    <p>Redness, heat, swelling, pain</p> Signup and view all the answers

    Name two types of professional phagocytes.

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

    What is the main function of natural killer cells?

    <p>Destroy virus-infected cells</p> Signup and view all the answers

    The ______ protein cascade may initiate the arrival of lymphocytes and antibodies.

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

    Fever is always a negative response to an infection.

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

    What is the name of the specific feature or portion of a molecule that the immune system responds to?

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

    MHC Class I proteins are found on all nucleated cells in the body.

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

    What are the three cell populations involved in adaptive immunity?

    <p>B lymphocytes, T lymphocytes, and antigen-presenting cells (APCs)</p> Signup and view all the answers

    Which of the following is NOT a primary lymphoid organ?

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

    All lymphocytes mature in the bone marrow.

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

    Explain the process of clonal selection in the context of adaptive immunity.

    <p>When an antigen is recognized by a lymphocyte with its specific receptor, that cell undergoes further development, proliferating and differentiating into a pool of identical cells with the same antigen-specific receptor, known as clones.</p> Signup and view all the answers

    What is the primary function of effector cells?

    <p>Directly attack invading pathogens</p> Signup and view all the answers

    Memory cells are only produced during a primary immune response.

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

    The ______ is considered to be a secondary lymphoid organ that filters blood and removes old red blood cells.

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

    What are the two main branches of the immune system?

    <p>Innate and adaptive immune responses</p> Signup and view all the answers

    What are the three lines of defense in the immune system?

    <p>Surface barriers, internal defenses and adaptive immune responses</p> Signup and view all the answers

    Innate immune responses are specific.

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

    What is the role of the surface barriers in the immune system?

    <p>The surface barriers, including the skin and mucous membranes, act as the first line of defense by preventing pathogens from entering the body.</p> Signup and view all the answers

    What is the role of the internal defenses?

    <p>Internal defenses are the second line of defense and they work to fight off pathogens that have managed to bypass the surface barriers.</p> Signup and view all the answers

    Which of the following are examples of internal defenses?

    <p>All of the above</p> Signup and view all the answers

    What is the main function of phagocytes?

    <p>Phagocytes engulf and destroy pathogens that have managed to bypass the surface barriers.</p> Signup and view all the answers

    What is the role of natural killer cells?

    <p>Natural killer cells are specialized lymphocytes that target and destroy infected cells and cancer cells.</p> Signup and view all the answers

    What are the benefits of inflammation?

    <p>Inflammation helps prevent the spread of pathogens, dispose of cellular debris, alert the adaptive immune system, and set the stage for tissue repair.</p> Signup and view all the answers

    What are the four cardinal signs of inflammation?

    <p>Redness, heat, swelling, and pain</p> Signup and view all the answers

    Impaired function is not considered a cardinal sign of inflammation.

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

    What are the main steps involved in the process of phagocytosis?

    <p>Phagocytosis involves adherence, engulfment, formation of a phagolysosome, digestion, and exocytosis.</p> Signup and view all the answers

    Fever is a good example of specific defense mechanisms.

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

    What does the term "opsonization" refer to?

    <p>Opsonization is the process of coating a pathogen with complement proteins, which makes it easier for phagocytes to engulf and destroy it.</p> Signup and view all the answers

    What is the role of the complement system in the immune response?

    <p>The complement system is a group of proteins that work together to destroy pathogens by enhancing phagocytosis and causing cell lysis via the Membrane Attack Complex (MAC).</p> Signup and view all the answers

    Interferons are virus-specific, meaning that a particular interferon can only target one specific virus.

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

    What is the primary function of interferons?

    <p>Interferons are proteins that play a vital role in protecting cells from viral infections by interfering with viral replication.</p> Signup and view all the answers

    How are interferons classified?

    <p>Interferons are classified into two types: Type I interferons (IFN-alpha, IFN-beta) and Type II interferon (IFN-gamma).</p> Signup and view all the answers

    What is the primary function of the adaptive immune response?

    <p>To recognize and destroy pathogens that have been encountered before</p> Signup and view all the answers

    The adaptive immune response is restricted to the initial site of infection.

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

    What is the role of memory in the adaptive immune system?

    <p>Memory allows the adaptive immune system to mount a faster and more potent response when exposed to a previously encountered pathogen.</p> Signup and view all the answers

    What are the two main components of the adaptive immune response?

    <p>Humoral immunity and cellular immunity.</p> Signup and view all the answers

    What is the role of B cells in the adaptive immune response?

    <p>B cells produce antibodies, which are proteins that bind to specific pathogens and help neutralize them.</p> Signup and view all the answers

    What is the role of T cells in the adaptive immune response?

    <p>T cells directly target and destroy infected or abnormal cells, contributing to cellular immunity.</p> Signup and view all the answers

    What is an antigen?

    <p>An antigen is any substance that can trigger an immune response.</p> Signup and view all the answers

    What is an epitope?

    <p>The specific region of an antigen that is recognized by antibodies or T cell receptors.</p> Signup and view all the answers

    What is the role of MHC proteins in the adaptive immune response?

    <p>MHC proteins present antigens to T cells, allowing them to recognize and respond to specific pathogens.</p> Signup and view all the answers

    What is the difference between complete antigens and incomplete antigens?

    <p>Complete antigens can trigger a full immune response by stimulating lymphocyte proliferation and antibody production. On the other hand, incomplete antigens, or haptens, cannot trigger a full immune response on their own and require binding to a carrier protein.</p> Signup and view all the answers

    What is the process of clonal selection?

    <p>Clonal selection is a process in which an antigen binds to the receptor of specific lymphocytes, triggering their proliferation and differentiation into effector cells and memory cells that are specifically targeted to fight off the pathogen.</p> Signup and view all the answers

    Lymphocytes are only found in the blood.

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

    What is the function of memory cells?

    <p>Memory cells are responsible for providing long-term immunity by quickly reactivating the immune response upon re-exposure to the same pathogen.</p> Signup and view all the answers

    B cells and T cells only circulate through the body during an active infection.

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

    Study Notes

    The Immune System

    • The immune system is a functional system, not an organ system.
    • It includes lymphoid organs, immune cells, and functional molecules.
    • Innate and adaptive responses are intertwined, both systems release and recognize the same/similar molecules.
    • Innate responses are largely non-specific, acting as the first and second lines of defense.
    • First line of defense: barriers like skin and mucous membranes.
    • Second line of defense: internal defenses like phagocytes, natural killer cells, inflammation, antimicrobial proteins, and fever.
    • Innate responses can initiate within minutes.
    • Adaptive defenses are specific, mounting attacks against foreign substances and acting as the third line of defense.
    • Adaptive responses take considerably more time to develop.
    • Adaptive defenses encompass humoral immunity (B cells) and cellular immunity (T cells).

    Surface Barriers (First Line of Defense)

    • Keratin in the epidermis resists weak acids and bases, bacterial enzymes, and toxins.
    • Cilia in the upper respiratory tract sweep potential pathogens/irritants towards the mouth.
    • Mucus membranes line body cavities that open to the exterior.
    • Acid mantle in skin, vagina, and stomach inhibits bacterial growth.
    • Lysozyme in saliva, respiratory mucus, and lacrimal fluid is antimicrobial.
    • Stomach enzymes digest proteins and kill microorganisms.
    • Mucin can trap microorganisms in thick mucus.
    • Thin watery mucus (saliva) can also wash them away.
    • Defensins are broad-spectrum antimicrobial peptides produced when surface barriers are breached.
    • Sweat components (e.g., dermicidin) are toxic to bacteria.

    Cells and Chemicals: Second Line of Defense (Innate)

    • Phagocytes engulf and destroy pathogens that breach surface barriers; macrophages also contribute to adaptive immune responses.
    • Natural killer (NK) cells promote apoptosis (cell death) in virus-infected or cancerous body cells and do not form memory cells.
    • Inflammatory response prevents injurious agents from spreading, disposes of pathogens and dead tissue cells, and promotes repair.
    • Antimicrobial proteins, like interferons, are released by virus-infected cells.
    • Complement proteins lyse microorganisms, enhance phagocytosis, intensify inflammatory responses, and contribute to tissue repair.
    • Fever increases body temperature, inhibiting microbes and enhancing repair.

    Phagocytes

    • Professional phagocytes include neutrophils, dendritic cells, macrophages, and mast cells.
    • Neutrophils are the most plentiful leukocytes.
    • Macrophages and dendritic cells derive from monocytes and patrol tissues/organs.
    • Non-professional phagocytes include epithelial, endothelial cells, and fibroblasts.

    Phagocytosis ('Cell Eating')

    • For phagocytes to ingest pathogens, they must adhere to the pathogen and recognize carbohydrate molecules on their surface.
    • Phagocytes form pseudopods to engulf the particles, forming a phagosome.
    • A lysosome fuses with the phagosome to form a phagolysosome.
    • Lysosomal enzymes digest the pathogens.
    • The residual body is then expelled from the cell.
    • Respiratory burst involves the release of destructive free radicals to kill microorganisms, increase acidity of the phagolysosome, and activate other anti-pathogen enzymes.

    Hematopoietic Cell Production

    • Hematopoiesis is the proliferation and differentiation of formed blood elements.
    • Stem cells differentiate to become various blood cells (e.g., erythrocytes, leukocytes, platelets).
    • Specialized cells like lymphocytes, monocytes etc. are formed.

    Natural Killer (NK) Cells

    • NK cells circulate in blood and lymph.
    • They are non-specific cells that lyse and kill cancer cells and virus-infected cells.
    • They identify abnormal cells by detecting abnormalities in cell protein expression (e.g., down-regulation or lack of MHC molecules).
    • Non-phagocytic; kill by direct contact with target cells, inducing apoptosis and secreting chemicals.

    Inflammation

    • Inflammation is a complex biological response to harm (e.g., tissue injury, intense heat, irritating chemicals, infection).
    • Benefits include preventing the spread of damaging agents, disposing of cell debris and pathogens, and alerting the adaptive immune system.
    • Four cardinal signs of inflammation are redness, heat, swelling, and pain.
    • Impaired function is a fifth possible cardinal sign.

    Inflammatory Chemical Release

    • Inflammatory processes begin with chemical alarms released by injured tissues and/or immune cells.
    • Macrophages use Toll-like receptors (TLRs) to recognize molecules associated with potential infection.
    • Various cytokines, kinins, prostaglandins, and complement proteins drive inflammation.

    Vasodilation & Increased Vascular Permeability

    • Inflammatory chemicals increase capillary permeability.
    • Exudate (fluid containing clotting factors and antibodies) enters tissue spaces, leading to swelling.
    • Edema has numerous benefits.
    • Fluid influx helps mobilize foreign material.
    • Clotting factors contribute to tissue repair and isolation of bacteria.
    • Some bacteria produce enzymes that break down clots, facilitating their spread.

    Phagocyte Mobilization

    • Phagocyte mobilization begins soon after the inflammatory response.
    • Neutrophils are the first to infiltrate the injured area.
    • Macrophages arrive subsequently.
    • Monocytes leave blood and become macrophages.
    • Phagocyte mobilization takes place in four steps: leukocytosis, margination, diapedesis, and chemotaxis.

    Antimicrobial Proteins

    • Antimicrobial proteins enhance innate defense by directly attacking microorganisms or hindering their ability to reproduce.
    • Interferons are named because they interfere with viral replication.
    • Complement System proteins enhances inflammation, opsonization, phagocytosis, and lysis of foreign cells.

    Interferons (IFNs)

    • IFNs produced against one virus may protect against other viruses.
    • Two classifications include Type I IFNs (IFN-alpha, IFN-beta) which primarily have antiviral effects and activate NK cells and Type II IFN (IFN-gamma) which is secreted by lymphocytes and activates macrophages.
    • IFNs play a role in cancer fighting and are therapeutically used to treat some viral infections.

    Complement System

    • The complement system consists of 20+ plasma proteins that circulate in inactive states.
    • It's a mechanism for destroying foreign substances (e.g., lysis and killing of bacteria).
    • Coating (opsonization) of pathogens enhances phagocytosis.
    • The complement system enhances both innate and adaptive immune defenses.
    • Activation of the complement system leads to inflammation, phagocytosis, and cell lysis via Membrane Attack Complex (MAC).

    Fever

    • Fever is an abnormally high body temperature due to a systemic response to invading microorganisms.
    • Release of pyrogens sets the 'physiological thermostat', in the hypothalamus, leading to a higher body temperature.
    • Benefits of fever include inhibiting microbial growth and speeding up repair processes.
    • Increased temperatures decrease iron/zinc availability to invading microorganisms.

    Adaptive Immune Response

    • The adaptive immune response is systemic and has memory, unlike the innate response.
    • Humoral immunity (antibody-mediated immunity) involves circulating antibodies produced by lymphocytes that bind to and target extracellular pathogens.
    • Cellular immunity (cell-mediated immunity) involves lymphocytes themselves defending against intracellular pathogens like viruses or parasites, and cancer cells/cells from transplanted organs.

    Antigens

    • An antigen is any substance that triggers an immune response.
    • The specific portion that triggers an immune response is called an antigenic determinant or epitope.
    • Antigens can be large complex molecules like proteins, carbohydrates, or nucleic acids.
    • Small molecules (haptens) need to bind to larger carrier proteins to be immunogenic.

    Self-Antigens: MHC Proteins

    • MHC proteins are glycoproteins present on the surface of all cells (except mature erythrocytes).
    • Alternative names also exist (e.g., HLA - Human Leukocyte Antigens).
    • MHC proteins are essential for self vs non self recognition and for presenting antigens to T-cells.

    Adaptive Immunity: Lymphocyte Development, Maturation & Activation

    • Lymphocytes arise from hematopoietic stem cells in bone marrow.
    • B cells mature in bone marrow, while T cells mature in the thymus.
    • Lymphocytes develop and undergo selection processes (positive selection, negative selection) for self-tolerance ensuring immunocompetence.
    • Antigen encounter and activation are crucial for lymphocyte activation, leading to proliferation and differentiation of effector cells (B cells — antibodies, T cells — direct/indirect killing) and memory cells.
    • Secondary lymphoid organs (e.g., lymph nodes, spleen) and circulation facilitate antigen encounters with lymphocytes.

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    Immune System: Part I PDF

    Description

    Test your knowledge on the innate immune system with this quiz. Explore key concepts such as antimicrobial proteins, the role of MHC proteins, and the mechanisms of inflammation. Determine which aspects of immunity are innate and how they function in defense against pathogens.

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