Innate Immunity Concepts Quiz
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Questions and Answers

Which component is cleaved by MASP-2 after MBL binds to a pathogen surface?

  • C3
  • C1q
  • C2
  • C4 (correct)
  • What role does C3b play in the complement system?

  • Cleaves C2 to activate further components
  • Promotes host damage
  • Inhibits the complement cascade
  • Acts as a 'tag' on the pathogen surface (correct)
  • What phenotype is associated with a deficiency in C2 complement components?

  • Sepsis from S. pneumoniae (correct)
  • Severe sepsis and other problems
  • Neisseria infections
  • Lupus
  • Which complement deficiency is associated with lupus?

    <p>C4</p> Signup and view all the answers

    Which outcome is indicated by host cells possessing inhibitors of complement?

    <p>Prevent host damage</p> Signup and view all the answers

    What role do tight junctions between epithelial cells play in innate immunity?

    <p>They create a physical barrier to prevent pathogen entry.</p> Signup and view all the answers

    Which component is most directly involved in the phagocytosis of pathogens?

    <p>C3b fragment</p> Signup and view all the answers

    How does a low pH in the stomach contribute to innate immunity?

    <p>It inhibits the growth of most pathogens.</p> Signup and view all the answers

    Which pathway of complement activation would likely be compromised in someone with defective lymphocyte function?

    <p>Classical pathway</p> Signup and view all the answers

    What is the primary function of antimicrobial factors secreted at epithelial surfaces?

    <p>To directly kill invading pathogens.</p> Signup and view all the answers

    What is the primary mediator released by mast cells that causes vasodilation and increases vascular permeability during inflammation?

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

    Which of the following is NOT one of the basic stages of acute inflammation?

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

    Which hallmark of inflammation is associated with increased blood flow leading to redness?

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

    What is the effect of acute inflammation on lymph flow?

    <p>It enhances lymph flow.</p> Signup and view all the answers

    According to historical medical observations, which of the following reflects the pain aspect of inflammation?

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

    What do PAMPs primarily indicate to the immune system?

    <p>The presence of conserved molecular structures from pathogens</p> Signup and view all the answers

    Which receptors are primarily responsible for recognizing DAMPs?

    <p>Pattern Recognition Receptors (PRRs)</p> Signup and view all the answers

    What is the function of the inflammasome complex formed by some NLRs?

    <p>To release IL-1β from cells</p> Signup and view all the answers

    What type of molecules can be classified as DAMPs?

    <p>Extracellular ATP</p> Signup and view all the answers

    Toll-like receptors (TLRs) are primarily involved in recognizing which type of ligands?

    <p>Extracellular microbial ligands</p> Signup and view all the answers

    What is one key feature of epithelial surfaces that aids in innate immunity?

    <p>Presence of tight junctions</p> Signup and view all the answers

    What triggers the complement system in the innate immune response?

    <p>Bacterial cell wall components</p> Signup and view all the answers

    Which cell types are primarily involved in the innate immune response?

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

    What is a characteristic of the acute inflammatory response?

    <p>Release of chemical mediators</p> Signup and view all the answers

    How does the innate immune system recognize 'non-self' entities?

    <p>By identifying damage-associated molecular patterns</p> Signup and view all the answers

    What distinguishes Pattern Recognition Receptors (PRRs) from other types of receptors in the immune system?

    <p>They are utilized to survey various compartments of the cell and body.</p> Signup and view all the answers

    Which of the following is a specific function of NOD-like receptors (NLRs)?

    <p>Inducing the release of cytokines and forming the inflammasome complex.</p> Signup and view all the answers

    Damage-Associated Molecular Patterns (DAMPs) primarily indicate what type of cellular state?

    <p>Cellular damage and stress.</p> Signup and view all the answers

    How many Toll-like Receptors (TLRs) are known to exist in humans?

    <p>10</p> Signup and view all the answers

    Which of the following correctly defines PAMPs?

    <p>Molecules associated with pathogens that trigger innate immune responses.</p> Signup and view all the answers

    What is a primary component that some active NLRs can induce?

    <p>Secretion of interleukins and other cytokines.</p> Signup and view all the answers

    Which type of immune cell primarily expresses Pattern Recognition Receptors?

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

    Which of the following is NOT a common example of a DAMP?

    <p>Bacterial membrane lipids</p> Signup and view all the answers

    What key response is primarily triggered by the activation of Toll-like Receptors (TLRs)?

    <p>Induction of pro-inflammatory genes</p> Signup and view all the answers

    What is one of the roles of extracellular heat-shock proteins in the context of DAMPs?

    <p>Signaling cellular stress and damage</p> Signup and view all the answers

    Study Notes

    Epithelial Barriers and Complement

    • Epithelial surfaces serve as primary physical barriers in innate immunity, lined with cells that create tight junctions to prevent pathogen entry.
    • Antimicrobial factors are secreted at epithelial surfaces, contributing to a hostile environment for pathogens.
    • The complement system plays a crucial role in the innate immune response, activated through various pathways, including the lectin pathway mediated by Mannose-Binding Lectin (MBL).
    • MBL binds pathogen surfaces, initiating a cascade that leads to the cleavage of complement proteins, ultimately tagging pathogens for destruction.

    Cells of Innate Immunity & Inflammation

    • Key innate immune cells include neutrophils and macrophages, which are essential for phagocytosis and the inflammatory response.
    • Neutrophils have a short lifespan but are abundant in blood and respond rapidly to infection.
    • Macrophages can reside in healthy tissues, have a longer lifespan, and initiate inflammation when damage occurs.
    • Cytokines released by activated macrophages and other cells enhance immune responses and inflammation.

    Inflammation Process

    • Acute inflammation involves three stages: dilation of small blood vessels, increased permeability of microvasculature, and leukocyte extravasation.
    • Symptoms of inflammation are characterized by Celsus’ hallmarks: redness (rubor), swelling (tumor), heat (calor), and pain (dolor).
    • Inflammation is a protective response but can also lead to various pathologies if dysregulated.

    Recognition of Non-Self and Damage

    • The innate immune system recognizes non-self entities through Pattern Recognition Receptors (PRRs), which detect Pathogen-Associated Molecular Patterns (PAMPs) and Damage-Associated Molecular Patterns (DAMPs).
    • PAMPs include microbial components like bacterial lipids and nucleic acids, whereas DAMPs consist of molecules released upon cell damage.
    • TLRs (Toll-Like Receptors) and NLRs (NOD-Like Receptors) are types of PRRs crucial for sensing microbial and damage signals, activating proinflammatory pathways.

    Complement System Outcomes and Deficiencies

    • The complement system enhances pathogen targeting via opsonization (C3b tagging), promoting phagocytosis and lysis of pathogens.
    • Complement deficiencies can lead to serious health issues: C1q deficiency is linked to lupus, C3 deficiency results in severe sepsis, and MAC deficiency predisposes to Neisseria infections.

    Inflammation – Acute vs Chronic

    • Acute inflammation typically results in edema and the recruitment of cells to combat pathogens, while chronic inflammation may lead to tissue damage and disease.

    Learning Objectives Recap

    • Distinguish between innate and adaptive immunity based on cell types and response kinetics.
    • Explain the contributions of epithelial barriers and the complement system.
    • Understand the importance of innate immune cells and the pathways leading to inflammation and tissue healing.
    • Elucidate how the innate immune system recognizes threats through specific receptors and mechanisms.

    Epithelial Barriers and Complement

    • Epithelial surfaces include skin, lungs, gastrointestinal (GI) tract, and reproductive tract, providing crucial defense against pathogens.
    • Epithelial tight junctions create a barrier that prevents pathogen entry, while mechanisms like mucociliary escalator and longitudinal flow contribute to mechanical protection.
    • Chemical defenses include low pH in the stomach, fatty acids in the skin, and antimicrobial enzymes like lysozyme in tears and saliva.
    • Healthy microbiomes in the skin, gut, and respiratory tract also play an essential role in innate immunity.

    Cells of Innate Immunity & Inflammation

    • Key innate immune cells:
      • Macrophages: Tissue-resident, long-lived, derived from blood monocytes, initiate immune responses.
      • Neutrophils: Short-lived, abundant, flood sites of inflammation to combat infection.
    • Both macrophages and neutrophils utilize phagocytosis, employing receptors and opsonization via complement and antibodies to facilitate particle uptake.

    Mechanisms of Phagocyte Action

    • Phagocytosis involves the fusion of phagosomes with lysosomes, leading to degradation of pathogens.
    • Reactive oxygen species are produced by key enzymes, NADPH oxidase and myeloperoxidase, essential for pathogen killing.
    • Deficiencies in these enzymes can result in Chronic Granulomatous Disease, characterized by recurrent infections.

    Complement System

    • Complement components participate in innate immune response to combat infection, triggered by various pathways.
    • Cleavage of C3 into C3a and C3b leads to:
      • Phagocytosis of pathogens via opsonization.
      • Lysis of pathogens through the formation of the membrane attack complex.
      • Activation of inflammatory responses, recruiting additional immune cells.

    Recognition of Non-Self and Damage

    • Pattern Recognition Receptors (PRRs) are essential for recognizing pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs).
    • PAMPs: Conserved microbial structures, such as bacterial membranes and viral nucleic acids, recognized for signaling an immune response.
    • DAMPs: Indicators of cellular damage, including extracellular heat-shock proteins and mitochondrial DNA.

    Pattern Recognition Receptors

    • Toll-Like Receptors (TLRs): Recognize extracellular microbial ligands; there are 10 TLRs in humans, inducing proinflammatory responses.
    • NOD-like Receptors (NLRs): Cytosolic receptors activated by PAMPs and DAMPs, with 22 family members linked to the inflammasome complex and IL-1β release.
    • PRRs are expressed by innate immune cells, activating them to initiate immune responses.

    Inflammatory Response

    • Acute inflammatory responses are characterized by key chemical mediators and cellular activities, aiding in pathogen clearance and healing.
    • Key mediators include various interleukins (IL-1, IL-2, IL-3), which contribute to the signaling processes in inflammation.

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    Description

    Test your knowledge on innate immunity, including epithelial barriers, complement systems, and the cells involved in innate immune responses. This quiz covers essential elements like innate recognition of non-self and damage, vital for understanding the immune system's first line of defense.

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