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Questions and Answers
What structure forms when a phagocyte engulfs a pathogen?
What structure forms when a phagocyte engulfs a pathogen?
What is the role of Toll-Like Receptors (TLRs) in phagocytosis?
What is the role of Toll-Like Receptors (TLRs) in phagocytosis?
How do some pathogens defend against phagocytic action?
How do some pathogens defend against phagocytic action?
Which mechanism allows Mycobacteria tuberculosis to survive within phagocytes?
Which mechanism allows Mycobacteria tuberculosis to survive within phagocytes?
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Why are pneumococcal vaccines effective against Streptococcus pneumoniae?
Why are pneumococcal vaccines effective against Streptococcus pneumoniae?
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What role do cytokines and chemokines play when tissue is damaged?
What role do cytokines and chemokines play when tissue is damaged?
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What structure is a common pathogen-associated molecular pattern (PAMP) found in gram-negative bacteria?
What structure is a common pathogen-associated molecular pattern (PAMP) found in gram-negative bacteria?
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What initiates the phosphorylation cascade in phagocytes during pathogenic recognition?
What initiates the phosphorylation cascade in phagocytes during pathogenic recognition?
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Which of the following accurately describes the role of diapedesis in the immune response?
Which of the following accurately describes the role of diapedesis in the immune response?
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What is the primary function of Toll-like receptors (TLRs) in leukocytes?
What is the primary function of Toll-like receptors (TLRs) in leukocytes?
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What is the role of opsonization in the complement system?
What is the role of opsonization in the complement system?
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How do natural killer cells identify and target virally infected cells?
How do natural killer cells identify and target virally infected cells?
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Which of the following about interferons is accurate?
Which of the following about interferons is accurate?
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What potential risk is associated with the anaphylatoxins C5a and C3a?
What potential risk is associated with the anaphylatoxins C5a and C3a?
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Which of the following components is involved in the direct attack of infected cells by NK cells?
Which of the following components is involved in the direct attack of infected cells by NK cells?
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What is the primary characteristic of innate immunity?
What is the primary characteristic of innate immunity?
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Which type of immunity is characterized by its acquired ability to recognize specific pathogens?
Which type of immunity is characterized by its acquired ability to recognize specific pathogens?
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What role do normal microbiota play in the immune system?
What role do normal microbiota play in the immune system?
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What is necessary for a pathogen to successfully colonize a host?
What is necessary for a pathogen to successfully colonize a host?
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Which pathogen is associated with cholera and the tissue it typically infects?
Which pathogen is associated with cholera and the tissue it typically infects?
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What is a key feature of adaptive immunity?
What is a key feature of adaptive immunity?
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Why might a pathogen fail to infect a specific tissue?
Why might a pathogen fail to infect a specific tissue?
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Which statement about the immune system is false?
Which statement about the immune system is false?
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What is the primary purpose of inflammation in response to pathogens?
What is the primary purpose of inflammation in response to pathogens?
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Which cytokine is primarily responsible for causing a rise in body temperature during a fever?
Which cytokine is primarily responsible for causing a rise in body temperature during a fever?
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How does fever help limit the growth of pathogens?
How does fever help limit the growth of pathogens?
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What can result from systemic inflammation and septic shock?
What can result from systemic inflammation and septic shock?
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What triggers a cytokine storm in response to Gram-negative bacteria?
What triggers a cytokine storm in response to Gram-negative bacteria?
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What initiates the classical pathway of complement activation?
What initiates the classical pathway of complement activation?
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What is NOT a characteristic of inflammation?
What is NOT a characteristic of inflammation?
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What is a possible consequence of increased vascular permeability during systemic inflammation?
What is a possible consequence of increased vascular permeability during systemic inflammation?
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Study Notes
Basic Properties of the Immune System
- Immunity is the ability of an organism to resist infection
- There are two types of immunity: innate and adaptive immunity
- Innate immunity is a built-in mechanism that doesn't require previous exposure to a pathogen
- Adaptive immunity is acquired and requires previous exposure to a pathogen or its products
- Adaptive immunity is directed toward specific molecular components of pathogens known as antigens
Barriers to Pathogen Invasion
- The normal microbiota of a host can help resist pathogens through competitive exclusion
- Pathogens may not successfully infect tissues due to incompatible nutritional and metabolic needs of the host
- Tissues have specific vulnerabilities to certain pathogens
- Infection routes determine which pathogens can infect which tissues
Microbial Invasion and the Innate Immune Response
- Tissue damage due to infection releases cytokines and chemokines
- Phagocytes, especially neutrophils, are attracted to infection sites by cytokines and chemokines
- Invading microorganisms are cleared through phagocytosis, restoring the tissue to health
Pathogen Recognition
- Pathogens possess structures and molecules not found in host cells, known as pathogen-associated molecular patterns (PAMPs)
- Examples of PAMPs include peptidoglycan, flagellin, dsRNA, and lipopolysaccharide (LPS)
- Leukocytes contain pattern recognition receptors (PRR) that recognize PAMPs
Phagocyte Signal Transduction
- Upon encountering PAMPs, Toll-like receptors (TLR) on phagocytes send a signal to the nucleus
- Each TLR recognizes a specific PAMP
- TLR activation results in a phosphorylation cascade that activates transcription factors in the nucleus
- Activated transcription factors lead to the production of proteins that induce inflammation and other phagocyte activities
Phagocytosis and Phagocyte Inhibition
- Phagocytes engulf pathogens upon recognizing PAMPs
- Engulfed bacteria are held within a membrane-bound vesicle called the phagosome
- Lysosomes fuse with the phagosome to form a phagolysosome
- Phagocytes generate toxic reactive oxygen intermediates to kill bacteria within the phagolysosome
- Some pathogens can survive the phagolysosome, such as Mycobacteria tuberculosis and Streptococcus pyogenes
- Some pathogens produce leukocidins, which kill white blood cells
- Some pathogens have capsules that make them difficult for phagocytes to engulf
Other Innate Host Defenses
- Inflammation is a nonspecific reaction to noxious stimuli
- Inflammation is characterized by redness, swelling, pain, and heat
- Cytokines and chemokines recruit white blood cells to the site of inflammation
- Effective inflammation isolates and limits tissue damage
- Fever is an increase in body temperature caused by cytokines like IL-1
- Fever can increase circulation rate, benefitting leukocyte movement
- Fever inhibits the growth of some pathogens
- Fever increases transferrin levels, which sequester iron from pathogens
- Systemic inflammation can lead to shock and organ damage
The Complement System
- The complement system (C') is a set of circulating, inactive proteins activated by pathogens
- The classical pathway of complement activation is initiated by antibodies binding to pathogens
- Complement activation results in opsonization, recruitment of phagocytes, and direct attack via the membrane attack complex (MAC)
- The mannose-binding lectin (MBL) and alternative pathways activate complement through innate mechanisms
- All three complement systems result in opsonization, direct attack, and phagocyte recruitment
Innate Defenses Against Viruses
- Natural killer (NK) cells are cytotoxic lymphocytes that recognize cells lacking MHC I proteins
- NK cells destroy target cells that lack MHC I and display stress proteins
- NK cells release granzyme, which induces apoptosis, and perforin, which perforates target membranes
- Interferons are small cytokine proteins produced by virally infected cells
- Interferons prevent viral replication by stimulating the production of antiviral proteins in uninfected cells
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Description
Explore the fundamental aspects of the immune system, including the differences between innate and adaptive immunity, and how barriers to pathogen invasion play a crucial role in maintaining health. This quiz covers the mechanisms of microbial invasion and the innate immune response, including the roles of cytokines and phagocytes.
