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Questions and Answers
What is one characteristic that differentiates innate immunity from adaptive immunity?
What is one characteristic that differentiates innate immunity from adaptive immunity?
Which type of immune cell is primarily responsible for the phagocytic barrier to infection?
Which type of immune cell is primarily responsible for the phagocytic barrier to infection?
Which complement pathway is not correctly matched with its characteristic?
Which complement pathway is not correctly matched with its characteristic?
What role do pattern recognition receptors (PRRs) play in innate immunity?
What role do pattern recognition receptors (PRRs) play in innate immunity?
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What is the primary function of neutrophils in the immune response?
What is the primary function of neutrophils in the immune response?
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What differentiates innate immunity's response to pathogens?
What differentiates innate immunity's response to pathogens?
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What is the function of antimicrobial peptides such as defensins?
What is the function of antimicrobial peptides such as defensins?
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Which of the following cell types have the ability to recognize and ingest pathogens via phagocytosis?
Which of the following cell types have the ability to recognize and ingest pathogens via phagocytosis?
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What role does sebum play in skin health?
What role does sebum play in skin health?
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How does lactobacillus contribute to vaginal health?
How does lactobacillus contribute to vaginal health?
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What is the primary role of hydrochloric acid secreted in the stomach?
What is the primary role of hydrochloric acid secreted in the stomach?
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Which of the following cells is crucial for acute infections?
Which of the following cells is crucial for acute infections?
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What is a mechanism used by phagocytic cells to recognize pathogens?
What is a mechanism used by phagocytic cells to recognize pathogens?
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What happens when lactobacillus is eliminated in the vagina due to antibiotics?
What happens when lactobacillus is eliminated in the vagina due to antibiotics?
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Which type of cell can perform both phagocytosis and pinocytosis?
Which type of cell can perform both phagocytosis and pinocytosis?
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What is the function of defensins secreted by respiratory cells?
What is the function of defensins secreted by respiratory cells?
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What method can be used to determine the phagocytic efficiency of neutrophils and macrophages?
What method can be used to determine the phagocytic efficiency of neutrophils and macrophages?
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What is indicated by the blue color in nitro blue tetrazolium (NBT) staining?
What is indicated by the blue color in nitro blue tetrazolium (NBT) staining?
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Which of the following statements is true regarding chronic granulomatous disease?
Which of the following statements is true regarding chronic granulomatous disease?
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What component of Gram-negative bacteria can activate the complement system?
What component of Gram-negative bacteria can activate the complement system?
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Which pathway activates complement through antigen-antibody complex formation?
Which pathway activates complement through antigen-antibody complex formation?
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What is the final structure formed in the complement cascade responsible for lysing bacterial cells?
What is the final structure formed in the complement cascade responsible for lysing bacterial cells?
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What is the enzyme in macrophages responsible for converting L-arginine to nitric oxide?
What is the enzyme in macrophages responsible for converting L-arginine to nitric oxide?
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Which factors are involved in the activation of the complement system in the alternate pathway?
Which factors are involved in the activation of the complement system in the alternate pathway?
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Which of the following best describes the role of mannose in complement activation?
Which of the following best describes the role of mannose in complement activation?
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What is the primary role of complement in innate immunity?
What is the primary role of complement in innate immunity?
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Which antimicrobial peptide in macrophages sequesters iron to deprive pathogens of a vital nutrient?
Which antimicrobial peptide in macrophages sequesters iron to deprive pathogens of a vital nutrient?
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Which factor inhibits the alternative pathway of complement activation?
Which factor inhibits the alternative pathway of complement activation?
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How does CD55 protect human cells from complement-mediated lysis?
How does CD55 protect human cells from complement-mediated lysis?
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What condition is associated with C1 inhibitor deficiency?
What condition is associated with C1 inhibitor deficiency?
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What is the fate of nitric oxide in macrophages after it is produced?
What is the fate of nitric oxide in macrophages after it is produced?
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Which of the following is NOT a method used by macrophages to control intracellular pathogens?
Which of the following is NOT a method used by macrophages to control intracellular pathogens?
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Which mechanism is NOT involved in the oxygen-independent control of intracellular pathogens by macrophages?
Which mechanism is NOT involved in the oxygen-independent control of intracellular pathogens by macrophages?
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What role does IL-8 play in the immune response involving macrophages?
What role does IL-8 play in the immune response involving macrophages?
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What happens due to an exacerbation of the complement cascade?
What happens due to an exacerbation of the complement cascade?
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What is a characteristic feature of macrophages concerning their cellular structure?
What is a characteristic feature of macrophages concerning their cellular structure?
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Which of the following factors plays a role in regulating both classical and alternate pathways of complement activation?
Which of the following factors plays a role in regulating both classical and alternate pathways of complement activation?
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What characteristic is associated with complement deficiency?
What characteristic is associated with complement deficiency?
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Which antimicrobial effect is attributed to lysozyme found in macrophages?
Which antimicrobial effect is attributed to lysozyme found in macrophages?
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Which mechanism is NOT involved in oxygen-independent killing by neutrophils?
Which mechanism is NOT involved in oxygen-independent killing by neutrophils?
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Study Notes
Introduction to Host Defense
- Key objective of lectures: Understand monocytes, macrophages, dendritic cells, and their immune functions.
- Monocytes differentiate into macrophages and dendritic cells, both crucial for innate immunity.
- Reactive oxygen species (ROS) are generated during the oxidative burst after tissue injury, aiding in pathogen elimination.
Innate Immune System
- Characteristics: pre-formed, active, non-specific, lacks immunological memory, does not improve over time.
- Innate immunity is often the first line of defense, but can be inadequate, prompting activation of adaptive immunity.
- Physical barriers include skin, mucous membranes, and secretions with antimicrobial properties, such as lysozyme.
Components of Innate Immunity
- Phagocytic cells: neutrophils (short-lived, target acute infections), macrophages (long-lived, handle acute and chronic infections), and dendritic cells (also long-lived, involved in antigen presentation).
- Neutrophils induce pus formation and utilize primary granules containing myeloperoxidase, lysozyme, and defensins.
- Macrophages generate superoxide and hydrogen peroxide but lack myeloperoxidase and thus produce no hypochlorous acid.
Role of Phagocytosis
- Phagocytic cells utilize pattern recognition receptors (PRRs) like TLR-2 and TLR-4 to identify pathogens.
- Intracellular killing mechanisms involve oxygen-dependent (oxidative burst) and oxygen-independent methods (lysosomal enzymes, defensins).
- Lysozyme disrupts the peptidoglycan layer in Gram-positive bacteria; lactoferrin sequesters iron, limiting pathogen growth.
Complement System
- Complement proteins become activated via three pathways: classical, alternative, and mannose-binding lectin pathway.
- Classical pathway starts with antigen-antibody complexes, resulting in the membrane attack complex (MAC) formation leading to bacterial lysis.
- Alternative pathway activates directly in the presence of Gram-negative bacteria's LPS.
- Complement functions include opsonization (tagging pathogens for phagocytosis) and aiding in inflammation.
Regulatory Mechanisms and Disorders
- Complement activation is tightly regulated by factors like C1 inhibitor, Factor H, and Factor I to prevent excessive inflammation.
- Deficiencies in components lead to increased susceptibility to infections, particularly Neisseria.
- Conditions such as chronic granulomatous disease arise from NADPH oxidase deficiencies, impairing the production of reactive oxygen species and increasing infection risk.
Comparisons in Immunity
- Innate immunity is fast but general; adaptive immunity is slower but provides targeted defense and immunological memory.
- Antigenicity refers to the ability of a substance to bind to an immune receptor, while immunogenicity is the ability to provoke an immune response.
Laboratory Techniques
- Phagocytic efficiency of neutrophils and macrophages can be tested with inert particles or pathogens observed microscopically post-staining.
- NADPH oxidase activity is assessed using nitro blue tetrazolium (NBT) staining to visualize free radical production.
Summary
- Understanding innate and adaptive immunity is crucial for identifying therapeutic interventions and managing immune-related diseases.
- Knowledge of phagocytic processes, complement activation, and regulatory mechanisms enhances appreciation for the body's immune defense strategies.
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Description
This quiz covers the fundamentals of host defense mechanisms, focusing on the roles of different immune cells such as monocytes, macrophages, and dendritic cells. Participants will learn about the reactive oxygen burst pathways and the comparative functions of neutrophils, monocytes, eosinophils, and basophils. Essential for understanding basic immunology and host responses to injury.