Lecture 03: Immune Response Overview {MCQ 2]
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Questions and Answers

Which of the following is NOT a direct effect of chemokines on leukocytes?

  • Chemotaxis towards the site of infection
  • Increased cell adhesion to the endothelium
  • Direct activation of phagocytic activity (correct)
  • Increased expression of high-affinity integrins

    • What is the primary function of Interleukin-1 (IL-1)?

  • Promoting the formation of blood clots
  • Triggering the differentiation of monocytes into macrophages
  • Inducing the expression of ICAMs on endothelial cells (correct)
  • Recruiting and activating neutrophils

    • Which of the following is the final step in the communication process mediated by cytokines?

  • Cytokine secretion
  • Binding to cytokine receptors
  • Biological effect on target cells (correct)
  • Cytokine gene activation

    • How do chemokines influence the movement of leukocytes during inflammation?

    <p>By creating a concentration gradient that attracts leukocytes (B)</p> Signup and view all the answers

    Which of the following is TRUE regarding the role of ICAMs in leukocyte recruitment?

    <p>ICAMs are expressed on endothelial cells and bind to leukocyte integrins. (B)</p> Signup and view all the answers

    What is the primary distinction between CC and CXC chemokines?

    <p>CC chemokines have two adjacent cysteine residues, while CXC chemokines have two cysteine residues separated by an amino acid. (A)</p> Signup and view all the answers

    What is the primary function of Tumor Necrosis Factor (TNF)?

    <p>Inducing the expression of chemokines on endothelial cells (B)</p> Signup and view all the answers

    Which of the following is the most likely consequence of a deficiency in Interleukin-8 (IL-8)?

    <p>Increased susceptibility to bacterial infections (C)</p> Signup and view all the answers

    Which of the following is a characteristic shared by cytokines and chemokines?

    <p>They both play a role in cell communication. (B)</p> Signup and view all the answers

    Which of the following best describes the role of leukocytes in the inflammatory response?

    <p>To recognize and destroy pathogens and remove cellular debris. (B)</p> Signup and view all the answers

    Which of the following statements about mast cells is NOT true?

    <p>They are primarily involved in adaptive immune responses, working with T lymphocytes to eliminate specific pathogens. (C)</p> Signup and view all the answers

    Which of the following is NOT a cardinal sign of inflammation?

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

    Which type of immune cell is most abundant in the blood, circulating for approximately 8 hours before dying?

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

    What is the primary role of chemokines in the inflammatory response?

    <p>Recruiting immune cells to the site of inflammation (A)</p> Signup and view all the answers

    Which of the following events occurs BEFORE an infection or injury?

    <p>Circulation of monocytes and neutrophils in the bloodstream (B)</p> Signup and view all the answers

    Which cell type is the first to encounter microbes in external barriers like skin and the gastrointestinal submucosal layer?

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

    What is the primary mechanism by which TNF (Tumor Necrosis Factor) contributes to inflammation?

    <p>Inducing vasodilation and increased capillary permeability (A)</p> Signup and view all the answers

    Which of the following events is directly responsible for the rolling of neutrophils along the endothelium during extravasation?

    <p>Binding of selectins to sugar molecules on neutrophil surfaces (A)</p> Signup and view all the answers

    How does the release of histamine by mast cells contribute to the inflammatory response?

    <p>Increasing blood flow to the site of inflammation (A)</p> Signup and view all the answers

    Which of the following best describes the role of PRRs (Pattern Recognition Receptors) in the inflammatory response?

    <p>Detecting conserved molecular structures on pathogens (B)</p> Signup and view all the answers

    Flashcards

    Inflammatory Response

    A complex biological response to infection or injury involving immune cell recruitment and tissue healing.

    Cardinal Signs of Inflammation

    Four primary indicators: redness, swelling, pain, and heat in affected tissues.

    Acute Inflammation

    Short-term inflammatory response to immediate infection or injury.

    Chronic Inflammation

    Long-term inflammatory response, often due to persistent injury or conditions like IBS or arthritis.

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    Neutrophils

    The most abundant type of white blood cell, short-lived and first responders to infection.

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    Macrophages

    Large phagocytic cells that engulf pathogens, found in tissues and derive from monocytes.

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    Dendritic Cells

    Tissue-resident cells that detect pathogens and activate immune response via cytokine release.

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    Mast Cells

    Tissue-resident cells that release histamine and initiate inflammation, linked to allergic responses.

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    Cytokines

    Proteins released by cells that communicate and regulate immune responses during inflammation.

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    Extravasation

    The process of immune cells leaving the bloodstream to enter tissues at the site of injury or infection.

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    ICAMs

    Intercellular Adhesion Molecules expressed by endothelial cells in response to cytokines.

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    Diapedesis

    The process of leukocytes moving through endothelial layers into tissues.

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    Chemokines

    A subgroup of cytokines that act as chemoattractants to guide immune cells to sites of infection.

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    Monocytes

    White blood cells that differentiate into macrophages to clear infections.

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    Cytokine family

    Various types of cytokines that act on specific receptors to elicit biological effects.

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    IL-1

    A pro-inflammatory cytokine that is released to initiate immune responses.

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    TNF

    Tumor Necrosis Factor, a cytokine involved in systemic inflammation.

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    CXC chemokines

    Chemokines that recruit neutrophils, indicated by separated CC residues.

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    Study Notes

    Inflammatory Response Overview

    • The inflammatory response is a complex cascade at the site of infection or injury, characterized by redness, swelling, pain, and heat (cardinal signs).
    • It's an acute (short-term) response to infection or a chronic (long-term) response to cell damage (e.g., IBS, arthritis).

    Immune Cell Types

    • Neutrophils: Most abundant, round cells with lobed nuclei. They circulate in the blood (alive ~8 hours). They're phagocytes.
    • Macrophages: Resident cells that are the first to encounter microbes. They're phagocytes. Found in external barriers (skin, GI tract, alveoli of lungs). Monocytes are recruited from the blood to differentiate into macrophages.
    • Dendritic cells: Resident in tissues. Sense danger and release cytokines.
    • Mast cells: Resident in skin and mucosal tissues. Activated by PAMPs, cytokines, or antibodies. Release histamine and cytokines, leading to vasodilation, increased capillary permeability and inflammation stimulation. Linked with allergic reactions.

    Inflammatory Response Steps

    • Before injury/infection: Monocytes and neutrophils circulate in the blood; resident macrophages, dendritic cells, and mast cells reside in tissues.
    • Injury/infection:
      • Local tissue damage and pain occur.
      • Bacteria enter.
      • Immune cells (e.g., innate), activated by PRRs (PAMPs), release cytokines.
      • Cytokines, chemokines, histamine, bioactive lipids (e.g., TNF, IL-8, IL-1) are released.
      • Damaged cells also release chemokines/cytokines.
    • Capillary Alterations: Vasodilation (increased capillary diameter) and increased capillary permeability (swelling/edema) happen due to histamine release by mast cells. Blood volume increases and blood flow slows down; inflammatory mediators enter the blood
    • Extravasation (Immune Cell Recruitment):
      • Step 1 (Rolling): Endothelial cells express cell adhesion molecules (e.g., selectins) on their surface, becoming sticky. Selectins bind to sugar molecules on neutrophil surfaces, resulting in weak temporary attachments.
      • Step 2 (Activation): Cytokines (e.g., TNF, IL-1) induce endothelial cells to express ICAMS. Chemokines cause leukocytes to express high affinity integrins. Integrin-ICAM interactions are strong (high avidity)
      • Step 3 (Arrest): Leukocytes adhere strongly to endothelial cells.
      • Step 4 (Diapedesis): Leukocytes cross into tissues. Chemokines (chemoattractants) indicate the site of infection.
    • Phagocytosis and Wound Clearance: Neutrophils respond first. Monocytes differentiate into macrophages to provide protection. Dendritic cells/macrophages travel to lymph nodes and present antigens. Clotting is part of the response.

    Inflammatory Mediators: Cytokines

    • Cytokines (e.g., IL-1, IL-8, TNF, Interferons) form a communication pathway between immune cells by using receptors.
    • Main functions:
      • Alter cell adhesiveness
      • Affect enzyme activity
      • Indicate whether cells live/die
      • Alter gene expression
    • Cytokine Family Steps:
      1. Inducing stimulus
      2. Cytokine gene activation
      3. Cytokine secretion
      4. Reaching cytokine receptors
      5. Signal transduction
      6. Gene/enzyme activation
      7. Biological effect (e.g., proliferation, differentiation, cell death)
    • Specific Cytokine Examples:
      • IL-1: Released by macrophages and epithelial cells. Binds to IL-1 receptors. Pro-inflammatory.
      • TNF: Released by macrophages and neutrophils. Binds to TNF receptors. Pro-inflammatory.
      • IL-8 (CXCL8): Recruits and activates neutrophils
    • Chemokines: A type of Cytokine:
      • Small cytokines with similar structure.
      • Cause cell adhesiveness and movement.
      • Generate chemotaxis (movement along a chemical gradient).
      • High concentration localized to site of infection.
      • Released during early infection by macrophages and damaged cells.
      • Classified based on conserved cysteine residues: CC and CXC.

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    Description

    Explore the fascinating mechanisms of the inflammatory response in this quiz. Delve into the roles of different immune cells such as neutrophils, macrophages, and dendritic cells, and understand how they contribute to both acute and chronic responses to infection. Test your knowledge and discover the intricate processes that protect our body from harm.

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