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Questions and Answers
What is the primary function of adaptive immunity in response to pathogens?
What is the primary function of adaptive immunity in response to pathogens?
Which type of microorganism is characterized as replicating outside the host's cells?
Which type of microorganism is characterized as replicating outside the host's cells?
What is a common consequence of the host's immune response to pathogens rather than the pathogens themselves?
What is a common consequence of the host's immune response to pathogens rather than the pathogens themselves?
How do some pathogens resist innate immunity?
How do some pathogens resist innate immunity?
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Which process is not associated with the infection caused by extracellular bacteria?
Which process is not associated with the infection caused by extracellular bacteria?
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Which of the following describes a characteristic of apoptosis?
Which of the following describes a characteristic of apoptosis?
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In what physiological processes does apoptosis occur?
In what physiological processes does apoptosis occur?
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What is a major difference between necrosis and apoptosis?
What is a major difference between necrosis and apoptosis?
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Which of the following factors is associated with necrosis?
Which of the following factors is associated with necrosis?
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What is the outcome of apoptotic cell death?
What is the outcome of apoptotic cell death?
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What role do CD4⁺ and CD8⁺ T cells play in immune response against intracellular bacteria?
What role do CD4⁺ and CD8⁺ T cells play in immune response against intracellular bacteria?
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How does the strain of Cryptococcus neoformans affect the immune response?
How does the strain of Cryptococcus neoformans affect the immune response?
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What is the primary innate immune response mechanism against fungi?
What is the primary innate immune response mechanism against fungi?
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What is apoptosis and why is it important in multicellular organisms?
What is apoptosis and why is it important in multicellular organisms?
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What is a characteristic of opportunistic fungal infections?
What is a characteristic of opportunistic fungal infections?
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What is the primary characteristic of endotoxins produced by Gram-negative bacteria?
What is the primary characteristic of endotoxins produced by Gram-negative bacteria?
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What role do cytokines play in the immune response against bacterial infections?
What role do cytokines play in the immune response against bacterial infections?
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What activates the alternative pathway of the complement system in extrinsic immunity?
What activates the alternative pathway of the complement system in extrinsic immunity?
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Which cytokine is the primary mediator of septic shock?
Which cytokine is the primary mediator of septic shock?
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What is a key mechanism of cell-mediated immunity against intracellular bacteria?
What is a key mechanism of cell-mediated immunity against intracellular bacteria?
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Why are intracellular bacteria resistant to phagocyte degradation?
Why are intracellular bacteria resistant to phagocyte degradation?
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What is the consequence of excessive cytokine production during a bacterial infection?
What is the consequence of excessive cytokine production during a bacterial infection?
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What distinguishes exotoxins from endotoxins?
What distinguishes exotoxins from endotoxins?
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Study Notes
Immune Response to Bacteria and Fungi
- Five categories of pathogenic microorganisms:
- Extracellular bacteria
- Intracellular bacteria
- Fungi
- Viruses
- Protozoa and multi-cellular parasites
General Overview of Immune Response to Microbes
- Although the body's immune response to microbes varies, several key aspects remain important.
- Innate immunity is the initial defense.
- Adaptive immunity builds upon innate immunity to provide stronger protection.
- Some pathogens evolve resistance to innate immunity, requiring adaptive immunity for protection.
Defense Mechanisms Against Microbes
- The immune system responds differently to various microbes, using distinct methods to fight infections effectively.
- Each microbe has distinct invasion and colonization patterns, requiring varied elimination strategies by different immune system components.
- The adaptive immune system allows the host to respond optimally.
Bacterial Infections and Tissue Damage
- Immune reactions to microbes, including bacterial products, often cause tissue damage and disease severity.
- Immune responses are crucial for fighting bacterial infections.
- Immune responses can also contribute to tissue damage during infections.
Bacterial Cell Walls
- Gram-positive and gram-negative bacteria have differing cell wall structures.
- Gram-positive bacteria have a thick peptidoglycan layer.
- Gram-negative bacteria have a thinner peptidoglycan layer with an outer membrane containing lipopolysaccharide (LPS).
Immunity to Extracellular Bacteria
- Extracellular bacteria replicate outside of host cells.
- Many bacterial species are pathogens.
- Mechanisms of infection include inflammation and toxin production.
- Endotoxins (e.g., LPS) are components of the bacterial cell wall.
- Exotoxins are actively secreted by bacteria.
- The effects of toxins may cause damage to neighboring host cells or tissues, leading to disease.
Mechanisms of Damage by Bacterial Toxins
- Exotoxins directly target and damage host cells.
- Endotoxins (LPS) act indirectly by triggering inflammation and host cell responses.
- These mechanisms result in damage to the host cell.
Innate Immunity to Extracellular Bacteria
- Complement activation, phagocytosis, and inflammation are central mechanisms in innate immunity against extracellular bacteria.
- Peptidoglycans activate the alternative pathway of complement.
- LPS activates the alternative pathway of complement.
- Activated phagocytosis leads to cytokine release.
- Cytokines activate leukocytes and cause normal tissue injury.
- Cytokines stimulate systemic responses like fever.
Adaptive Immunity to Extracellular Bacteria
- Humoral immunity plays a major role in fighting extracellular bacteria.
- Antibodies directly target bacterial cells to block infection, eliminate the microbes, and neutralize toxins.
- Antibodies activate complement system via classical pathways to assist in clearing bacteria.
Septic Shock
- Septic shock is a severe consequence of bacterial infections, with gram-positive and gram-negative bacteria.
- Characterized by circulatory collapse.
- Disseminated intravascular coagulation (DIC): systemic blood clotting
Examples of Extracellular Pathogenic Bacteria
- Staphylococcus aureus
- Streptococcus pyogenes
- Streptococcus pneumoniae
- Escherichia coli
- Vibrio cholerae
- Clostridium tetani
- Neisseria meningitidis
- Corynebacterium diphtheriae
Immunity to Intracellular Bacteria
- Intracellular bacteria survive and replicate within host cells.
- These bacteria often evade circulating antibodies, requiring cell-mediated immunity for elimination.
Innate Immunity to Intracellular Bacteria
- Phagocytes (like macrophages and neutrophils) ingest and destroy bacteria.
- Intracellular bacteria may resist degradation by phagocytes.
- Bacteria trigger an immune response leading to NK cell activation and enhanced phagocytosis by macrophages.
Cell-Mediated Immunity
- Cell-mediated immunity consists of two main reactions:
- Macrophage activation by T cell-derived signals (e.g., CD40L).
- Activation by IFN-γ.
- Resulting in the killing of intracellular microbes and infected cells.
Examples of Intracellular Pathogenic Bacteria
- Mycobacteria (e.g., Tuberculosis, Leprosy)
- Listeria monocytogenes
- Legionella pneumophilia
Immunity to Fungi
- Fungal infections (mycoses) can cause morbidity and mortality.
- Some fungi are endemic, existing in the environment and potentially inhaled.
- Certain fungal infections are opportunistic, occurring only in immunocompromised individuals.
Innate Immunity to Fungi
- Neutrophils and macrophages are involved in fungal defense.
- Neutrophils are highly effective against fungi due to ROS and lysosomal enzymes.
Adaptive Immunity to Fungi, Special Cases
- Some fungal strains, like Cryptococcus neoformans, inhibit cytokine production by macrophages.
- Cell-mediated immunity is a primary mechanism of defense against fungi.
Examples of Fungal Pathogens
- Candida albicans
- Aspergillus fumigatus
- Histoplasma capsulatum
Cell Death Mechanisms
Apoptosis
- A physiological process for programmed cell death, crucial in multicellular organisms, particularly during development and metamorphosis.
- A Greek word meaning "falling off".
- The cellular processes for apoptosis include cell shrinkage, chromatin condensation, and formation of apoptotic bodies.
Apoptosis's Key Roles
- Essential to embryonic development.
- Crucial for maintaining homeostasis of tissues.
- Important for regulating tissue structure and function, in both physiological and pathological conditions.
Necrosis
- A pathological process of cell death, often triggered by injury.
- It differs from apoptosis, exhibiting incompletely regulated enzyme digestion of cellular components.
- Necrosis leads to inflammation due to leakage of cellular products.
Mechanisms and Processes of Cell Death
- Normal cells respond to stress through adaptive mechanisms or cell death, like apoptosis or necrosis.
- Cell damage and failure to adapt can lead to reversible or irreversible cell injuries.
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Description
Explore the body's immune response to various pathogens, including bacteria and fungi. Learn about the differences between innate and adaptive immunity and how the immune system employs specific strategies against different types of microorganisms. This quiz covers the mechanisms of defense critical for understanding infections.
