Chapter 17: Innate Non-Specific Host Defenses

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Questions and Answers

What initiates the inflammation process?

  • Recruitment of neutrophils to tissues
  • Formation of a fibrin clot
  • Activation of the complement system
  • Release of cytokines by macrophages (correct)

Which mechanism directly leads to fluid accumulation during inflammation?

  • Formation of complement proteins
  • Vasodilation of capillary walls (correct)
  • Activation of cytokines
  • Recruitment of phagocytes

What is the primary function of a fibrin clot in the inflammatory response?

  • To enhance phagocytosis
  • To prevent the spread of infection (correct)
  • To promote cytokine release
  • To inhibit vasodilation

Pyrogens are substances classified as what?

<p>Substances that induce fever by acting on the hypothalamus (D)</p> Signup and view all the answers

Which mechanism describes the process of marking pathogens for phagocytosis?

<p>The marking of pathogens for phagocytosis (B)</p> Signup and view all the answers

In terms of inflammation, what does edema refer to?

<p>The accumulation of fluid in tissues (D)</p> Signup and view all the answers

Which signaling type is associated with cytokines that affect nearby cells?

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

Which acute-phase protein is responsible for binding and sequestering iron?

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

Which antimicrobial peptide secreted by salivary glands disrupts intracellular function?

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

What role do chemokines serve in innate immunity?

<p>To attract neutrophils and macrophages to infected tissue (A)</p> Signup and view all the answers

What distinguishes the paracrine signaling mechanism from other signaling types?

<p>Signals are secreted and act on adjacent cells. (A)</p> Signup and view all the answers

Which type of immune cell is primarily responsible for the rapid response in the initial stage of infection?

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

What role do chemokines play during the inflammatory response?

<p>They attract phagocytes to the site of infection. (C)</p> Signup and view all the answers

What is the primary function of interleukins in the immune system?

<p>To facilitate communication between different immune cells. (A)</p> Signup and view all the answers

Which of the following best describes the role of microbiota in innate immunity?

<p>They compete with pathogens for nutrients and space. (B)</p> Signup and view all the answers

Which of the following statements about natural killer (NK) cells is accurate?

<p>They destroy infected cells without prior sensitization. (C)</p> Signup and view all the answers

What is the primary function of lysozyme found in tears and saliva?

<p>To target and break down Gram-positive peptidoglycan. (B)</p> Signup and view all the answers

In the context of phagocytosis, what does opsonization refer to?

<p>The marking of pathogens to enhance ingestion. (B)</p> Signup and view all the answers

What is a primary characteristic of macrophages in the immune system?

<p>Phagocytic activity and long-term presence. (D)</p> Signup and view all the answers

Which component is NOT considered a physical barrier in the innate immune system?

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

Which type of cytokine is primarily involved in the antiviral response?

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

What function do acute phase proteins serve in the innate immune response?

<p>Coat bacteria to prepare them for ingestion. (B)</p> Signup and view all the answers

Which component of blood is crucial in forming a fibrin clot to prevent the spread of infection?

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

What is the primary role of the complement system in innate immunity?

<p>To enhance phagocytosis, inflammation, and pathogen lysis. (B)</p> Signup and view all the answers

Which type of immunity is characterized by specific resistance to pathogens?

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

What is the primary role of pyrogens in the body?

<p>To induce fever by acting on the hypothalamus. (C)</p> Signup and view all the answers

What is the primary role of defensins in innate immunity?

<p>To disrupt the membranes of various pathogens. (B)</p> Signup and view all the answers

Which of the following best describes the function of cytokines in the immune response?

<p>They act as signaling proteins to recruit immune cells. (D)</p> Signup and view all the answers

Which of the following is NOT a function of plasma protein mediators in innate immunity?

<p>Disrupting intracellular functions of viruses. (A)</p> Signup and view all the answers

What is a primary characteristic of the 1st line of defense in innate immunity?

<p>It consists of physical and chemical barriers. (D)</p> Signup and view all the answers

Flashcards

Immunity

The body's ability to resist disease.

Immune system

A collection of cells, tissues, and molecules that make up the body's defense system.

Immunology

The study of how the immune system works.

Innate Immunity

Pre-existing defenses present at birth, providing non-specific resistance against pathogens.

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1st line of defense

The first line of defense against pathogens; includes physical barriers like skin and mucous membranes.

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2nd line of defense

The second line of defense against pathogens; includes white blood cells, inflammation, and antimicrobial substances.

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Acquired Immunity

Specific resistance to pathogens, developed after exposure.

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3rd line of defense

The third line of defense, targeting specific pathogens by recognizing antigens.

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Antigen

A protein that triggers an immune response.

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Inflammation

A process that destroys pathogens and repairs damaged tissue.

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Autocrine Signaling

Cell releases a cytokine signal that binds to receptors on the same cell, triggering a response within the cell.

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Paracrine Signaling

Cell releases a cytokine signal that targets nearby cells, causing a localized response.

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Endocrine Signaling

Cell releases a cytokine signal that travels through the bloodstream to reach distant target cells throughout the body.

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Phagocytosis

A process where immune cells like macrophages engulf and destroy foreign particles, pathogens, and cellular debris.

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Pyrogens

Substances that induce fever by acting on the hypothalamus in the brain.

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Opsonization

The process of marking pathogens with opsonins, which are proteins that enhance phagocytosis by marking pathogens for immune cell targeting.

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What are pyrogens?

Molecules that induce fever by acting on the hypothalamus, the part of the brain that regulates body temperature.

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What is opsonization?

The process of marking pathogens for phagocytosis, making them more recognizable and easily engulfed by phagocytes.

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What does edema refer to in the context of inflammation?

The accumulation of fluid in tissues, often occurring during inflammation due to increased vascular permeability.

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Which cytokine signal is secreted to the same cell?

A type of cytokine signaling where the signaling molecule acts on the same cell that released it.

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Which acute-phase protein binds iron to inhibit pathogen growth?

An acute-phase protein that binds and sequesters iron, making it unavailable to pathogens and inhibiting their growth.

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Which antimicrobial peptide disrupts intracellular function?

Antimicrobial peptides secreted by salivary glands that disrupt intracellular function, primarily by disrupting the cell membrane.

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What is the role of chemokines in innate immunity?

Small secreted proteins that act as chemoattractants, drawing immune cells like neutrophils and macrophages to the site of infection.

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Where do blood platelets originate from?

Blood platelets originate within the bone marrow.

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Which granulocyte is concentrated in the skin, lungs, and GI tract?

Neutrophils are a type of granulocyte concentrated in the skin, lungs, and GI tract, acting as the first line of defense.

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What triggers the initiation of inflammation?

The release of cytokines by macrophages triggers the initiation of inflammation.

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Study Notes

Innate Non-Specific Host Defenses Study Notes

  • Immunity: The body's ability to resist disease.
  • Immune System: Collection of cells, tissues, and molecules protecting the body from pathogens.
  • Immunology: Scientific study of the immune system's function.
  • Innate Immunity: Nonspecific, inborn defense mechanisms.
  • 1st Line of Defense: Physical barriers (skin, mucous membranes/secretions).
  • 2nd Line of Defense: White blood cells, inflammation, antimicrobial substances.
  • Acquired Immunity: Specific resistance, with memory and targeted response.
  • 3rd Line of Defense: Antigen-specific defenses targeting particular pathogens.

Physical Barriers

  • Skin: Keratinized barrier, sheds microbes, compromised skin allows entry.
  • Mucous Membranes: Line internal tracts (respiratory, digestive, urogenital).
  • Mechanical Defenses: Flushing (tears, urine), mucus trapping/expelling pathogens.
  • Microbiota: Competes with pathogens for resources (nutrients, space).

Chemical Barriers

  • Enzymatic Mediators:
    • Lysozyme: Tears, saliva; targets Gram-positive peptidoglycan.
    • Digestive Enzymes: (amylase, bile, lipase) in saliva, stomach acid.
  • Lactoferrin: Sequesters iron, inhibits pathogen growth.
  • Antimicrobial Peptides:
    • Bacteriocins: Secreted by microbiota, disrupt membranes.
    • Cathelicidin, Defensins, Dermicidin: Secreted by skin cells; disrupt microbial membranes.
    • Histatins: Secreted by salivary glands; disrupt intracellular function.
  • Plasma Protein Mediators (produced in liver):
    • Acute Phase Proteins:
      • C-reactive protein/Serum amyloid A: Coats bacteria for ingestion.
      • Ferritin/transferrin: Bind & sequester iron, inhibiting growth.
      • Fibrinogen: Forms blood clots.
      • Mannose-binding lectin: Activates complement cascade.
  • Complement System: Enhances phagocytosis, inflammation, and pathogen lysis (effective against Gram-negative bacteria).
  • Opsonins: Enhance phagocytosis by marking pathogens for recognition.
  • Cytokines: Signaling proteins, recruiting immune cells, antiviral actions. (Autocrine, paracrine, endocrine signaling mechanisms).
    • Interleukins: Stimulate most immune functions.
    • Chemokines: Stimulate migration of neutrophils/macrophages to infected tissues.
    • Interferons: Trigger macrophage activation, interfere with RNA viral reproduction.

Cellular Barriers

  • Blood: Fluid, clotting agents.
  • Serum: Fluid portion of blood.
  • Blood Platelets: Small, disk-shaped cells from bone marrow.
  • Granulocytes: Initial infection stage, concentrated in skin, lungs, and GI tracts.
    • Neutrophils: First responders, short lifespan.
  • Agranulocytes:
    • Monocytes: Single nucleus, phagocytic after leaving bloodstream.
    • Macrophages: Mature monocytes, effective long-term phagocytosis.
    • Dendritic Cells: Link innate and acquired immunity.
    • Natural Killer (NK) Cells: Attack and destroy cancer/infected cells without prior sensitization. (release perforins & granzymes)

Phagocytosis and Inflammation

  • Phagocytosis: Immune cells capturing & digesting foreign particles.
  • Inflammation: Response to infection, tissue damage.
  • Steps of Inflammation:
    • Initiation: Macrophages release cytokines.
    • Vasodilation: Capillaries dilate, fluid accumulation (edema).
    • Phagocyte Recruitment: Chemokines attract phagocytes.
    • Formation of Fibrin Clot: Prevents infection spread.

Other Key Concepts

  • Pyrogens: Substances that induce fever.
  • Edema: Fluid accumulation due to vasodilation.

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