Podcast
Questions and Answers
In the context of immune self-recognition, what is the most critical implication of a host cell exhibiting reduced or absent MHC class I molecule expression in conjunction with detectable stress signals?
In the context of immune self-recognition, what is the most critical implication of a host cell exhibiting reduced or absent MHC class I molecule expression in conjunction with detectable stress signals?
- It triggers the release of regulatory cytokines, such as IL-10 and TGF-β, to dampen potential autoimmune responses.
- It compromises the cell's ability to interact successfully with other cells, impairing essential immune functions.
- It induces a compensatory upregulation of MHC class II molecules, enhancing antigen presentation to CD4+ T helper cells.
- It flags the cell as a target for elimination by natural killer (NK) cells, indicative of viral infection or malignant transformation. (correct)
How do pattern recognition receptors (PRRs) orchestrate an immune response upon encountering pathogen-associated molecular patterns (PAMPs) in a previously unexposed host?
How do pattern recognition receptors (PRRs) orchestrate an immune response upon encountering pathogen-associated molecular patterns (PAMPs) in a previously unexposed host?
- By directly activating the complement cascade via the classical pathway, leading to opsonization and lysis of the pathogen.
- By presenting processed PAMP peptides on MHC class II molecules to stimulate naive CD4+ T helper cells, initiating a T cell-dependent adaptive immune response.
- By initiating V(D)J recombination in B and T lymphocytes to generate antibodies and T cell receptors specific to the encountered PAMPs. (correct)
- By triggering intracellular signaling cascades that induce the expression of inflammatory cytokines and chemokines, thus activating innate immune cells.
In the context of immunologic memory, what is the most critical distinction between the responses of memory T cells and naive T cells upon re-encountering their cognate antigen?
In the context of immunologic memory, what is the most critical distinction between the responses of memory T cells and naive T cells upon re-encountering their cognate antigen?
- Memory T cells undergo a process of clonal deletion to prevent hyperactivation, whereas naive T cells undergo clonal expansion.
- Memory T cells primarily secrete regulatory cytokines such as IL-10 to suppress inflammation, while naive T cells primarily secrete pro-inflammatory cytokines.
- Memory T cells require co-stimulation through CD28, whereas naive T cells can be activated solely through TCR signaling. (correct)
- Memory T cells exhibit altered trafficking patterns, allowing for more rapid migration to sites of inflammation compared to naive T cells.
Given the multifaceted defense strategies employed by the immune system, what is the most critical advantage provided by the formation of granulomas in response to persistent intracellular pathogens such as Mycobacterium tuberculosis?
Given the multifaceted defense strategies employed by the immune system, what is the most critical advantage provided by the formation of granulomas in response to persistent intracellular pathogens such as Mycobacterium tuberculosis?
Suppose a novel virus emerges that is capable of directly inhibiting MHC class I molecule expression in infected host cells. What is the most likely consequence of this viral immune evasion strategy?
Suppose a novel virus emerges that is capable of directly inhibiting MHC class I molecule expression in infected host cells. What is the most likely consequence of this viral immune evasion strategy?
Bacterial pathogens employ diverse strategies to evade host immune defenses. What represents the most significant advantage conferred by molecular mimicry, where bacterial surface structures resemble host molecules?
Bacterial pathogens employ diverse strategies to evade host immune defenses. What represents the most significant advantage conferred by molecular mimicry, where bacterial surface structures resemble host molecules?
What is the functional significance of T helper cells in adaptive immunity?
What is the functional significance of T helper cells in adaptive immunity?
Consider a scenario where a previously healthy individual develops a novel mutation that impairs the function of their Toll-like receptors (TLRs). What is the most likely consequence of this mutation on their immune response?
Consider a scenario where a previously healthy individual develops a novel mutation that impairs the function of their Toll-like receptors (TLRs). What is the most likely consequence of this mutation on their immune response?
In the context of immune responses to viral infections, what is the most critical role of cytotoxic T lymphocytes (CTLs) in resolving the infection and preventing chronic disease?
In the context of immune responses to viral infections, what is the most critical role of cytotoxic T lymphocytes (CTLs) in resolving the infection and preventing chronic disease?
What is the most accurate description of the evolutionary trade-off between the speed and specificity of the innate and adaptive immune systems?
What is the most accurate description of the evolutionary trade-off between the speed and specificity of the innate and adaptive immune systems?
Given the process of central tolerance in T cell development, what is the most significant implication of the deletion of T cells that react strongly with self-antigens presented on MHC molecules in the thymus?
Given the process of central tolerance in T cell development, what is the most significant implication of the deletion of T cells that react strongly with self-antigens presented on MHC molecules in the thymus?
In the context of B cell development and antibody production, what is the functional significance of somatic hypermutation in the germinal center reaction?
In the context of B cell development and antibody production, what is the functional significance of somatic hypermutation in the germinal center reaction?
Considering the role of regulatory T cells (Tregs) in maintaining immune homeostasis, what is the most critical mechanism by which Tregs suppress immune responses and prevent autoimmunity?
Considering the role of regulatory T cells (Tregs) in maintaining immune homeostasis, what is the most critical mechanism by which Tregs suppress immune responses and prevent autoimmunity?
Given the importance of antigen presentation in initiating adaptive immune responses, what is the most significant distinction between the processing and presentation of antigens by MHC class I and MHC class II molecules?
Given the importance of antigen presentation in initiating adaptive immune responses, what is the most significant distinction between the processing and presentation of antigens by MHC class I and MHC class II molecules?
What is the most critical consequence of immune checkpoint blockade therapies (e.g., anti-CTLA-4 and anti-PD-1 antibodies) in the context of cancer immunotherapy?
What is the most critical consequence of immune checkpoint blockade therapies (e.g., anti-CTLA-4 and anti-PD-1 antibodies) in the context of cancer immunotherapy?
Considering the potential risks associated with passive antibody therapy, what is the most concerning complication arising from the administration of intravenous immunoglobulin (IVIG) prepared from pooled plasma of thousands of donors, especially in immunocompromised individuals?
Considering the potential risks associated with passive antibody therapy, what is the most concerning complication arising from the administration of intravenous immunoglobulin (IVIG) prepared from pooled plasma of thousands of donors, especially in immunocompromised individuals?
What is the significance of Natural Killer (NK) cells in the context of antiviral immunity?
What is the significance of Natural Killer (NK) cells in the context of antiviral immunity?
The process of clonal selection is crucial for adaptive immunity. How does clonal selection contribute to the specificity and effectiveness of the immune response?
The process of clonal selection is crucial for adaptive immunity. How does clonal selection contribute to the specificity and effectiveness of the immune response?
What is the best strategy that microorganisms can use to resist a host?
What is the best strategy that microorganisms can use to resist a host?
Microbes secrete high doses of antigens into the bloodstream. What is the intended effect of this mechanism?
Microbes secrete high doses of antigens into the bloodstream. What is the intended effect of this mechanism?
Microbes are able to coat themselves with host proteins such as fibronectin and antibodies. What is the resulting action?
Microbes are able to coat themselves with host proteins such as fibronectin and antibodies. What is the resulting action?
How does the immune system recognize non-self?
How does the immune system recognize non-self?
Contrast how the innate and adaptive immune systems deal with subsequent encounters with stimuli.
Contrast how the innate and adaptive immune systems deal with subsequent encounters with stimuli.
Choose the statement that most accurately describes the nature of the innate immune system.
Choose the statement that most accurately describes the nature of the innate immune system.
What is the most important method of achieving active immunity?
What is the most important method of achieving active immunity?
What are the main properties of acquired and passive immunity?
What are the main properties of acquired and passive immunity?
In the context of a bacterial skin infection leading to abscess formation, what is the MOST ACCURATE description of the role of fibrinogen in this process?
In the context of a bacterial skin infection leading to abscess formation, what is the MOST ACCURATE description of the role of fibrinogen in this process?
What is the most crucial distinction between active and passive immunity regarding the duration of protection and the mechanism of action?
What is the most crucial distinction between active and passive immunity regarding the duration of protection and the mechanism of action?
What would be the MOST LIKELY outcome if a person lacked the ability to produce somatically generated receptors?
What would be the MOST LIKELY outcome if a person lacked the ability to produce somatically generated receptors?
What is the significance of immunologic memory in the adaptive immune system?
What is the significance of immunologic memory in the adaptive immune system?
What is the MOST important consequence of the absence of self indicators on cells?
What is the MOST important consequence of the absence of self indicators on cells?
How does the ability to recognize something that is not self and has not been seen represents a challenge?
How does the ability to recognize something that is not self and has not been seen represents a challenge?
How is the specificity of the adaptive immune system mediated?
How is the specificity of the adaptive immune system mediated?
How do pathogens trick force of the immunological response.
How do pathogens trick force of the immunological response.
What is the function of cells in the complement system?
What is the function of cells in the complement system?
With respect to immunization, which agent requires a host-pathogen interaction.
With respect to immunization, which agent requires a host-pathogen interaction.
What is the long term result from active immunization?
What is the long term result from active immunization?
What does the immune system do once it decides to eliminate a threat?
What does the immune system do once it decides to eliminate a threat?
Considering the stochastic nature of V(D)J recombination and junctional diversity, what is the probability that two unrelated individuals will generate a T cell receptor (TCR) with identical complementarity-determining region 3 (CDR3) sequences capable of recognizing the same cognate antigen presented on an identical MHC molecule?
Considering the stochastic nature of V(D)J recombination and junctional diversity, what is the probability that two unrelated individuals will generate a T cell receptor (TCR) with identical complementarity-determining region 3 (CDR3) sequences capable of recognizing the same cognate antigen presented on an identical MHC molecule?
Given the intricate interplay between innate and adaptive immunity, what is the most likely outcome of a mutation that selectively ablates the capacity of dendritic cells to migrate from peripheral tissues to secondary lymphoid organs?
Given the intricate interplay between innate and adaptive immunity, what is the most likely outcome of a mutation that selectively ablates the capacity of dendritic cells to migrate from peripheral tissues to secondary lymphoid organs?
If a pharmaceutical company aims to develop a novel adjuvant to enhance vaccine efficacy, what molecular target would provide the most comprehensive stimulation of both innate and adaptive immune responses, while minimizing the risk of inducing autoimmunity?
If a pharmaceutical company aims to develop a novel adjuvant to enhance vaccine efficacy, what molecular target would provide the most comprehensive stimulation of both innate and adaptive immune responses, while minimizing the risk of inducing autoimmunity?
Considering the principle of immunological tolerance, what is the most critical factor determining whether a self-antigen expressed in the thymus will induce central tolerance (T cell deletion or development of regulatory T cells) versus triggering autoimmunity in the periphery?
Considering the principle of immunological tolerance, what is the most critical factor determining whether a self-antigen expressed in the thymus will induce central tolerance (T cell deletion or development of regulatory T cells) versus triggering autoimmunity in the periphery?
Given the complexities of immune responses against intracellular pathogens, what is the most critical factor determining the efficacy of a CD8+ T cell-mediated response in clearing a persistent viral infection?
Given the complexities of immune responses against intracellular pathogens, what is the most critical factor determining the efficacy of a CD8+ T cell-mediated response in clearing a persistent viral infection?
In the context of cancer immunotherapy, what represents the most significant challenge in engineering a chimeric antigen receptor (CAR) T cell therapy that can effectively eradicate solid tumors while minimizing off-target toxicity?
In the context of cancer immunotherapy, what represents the most significant challenge in engineering a chimeric antigen receptor (CAR) T cell therapy that can effectively eradicate solid tumors while minimizing off-target toxicity?
Considering the intricate mechanisms of immune regulation, what is the most likely consequence of a genetic defect that selectively impairs the function of FoxP3+ regulatory T cells (Tregs) in an otherwise healthy individual?
Considering the intricate mechanisms of immune regulation, what is the most likely consequence of a genetic defect that selectively impairs the function of FoxP3+ regulatory T cells (Tregs) in an otherwise healthy individual?
Given the diverse mechanisms of immune evasion employed by pathogens, what is the most significant advantage conferred by a virus that establishes latency within long-lived hematopoietic stem cells?
Given the diverse mechanisms of immune evasion employed by pathogens, what is the most significant advantage conferred by a virus that establishes latency within long-lived hematopoietic stem cells?
In the context of transplantation immunology, what is the most critical factor determining the long-term survival of an allogeneic organ graft?
In the context of transplantation immunology, what is the most critical factor determining the long-term survival of an allogeneic organ graft?
Considering the principles of vaccine design, what is the most significant advantage of using a recombinant viral vector vaccine that expresses multiple conserved epitopes from a highly variable virus, such as HIV, compared to traditional subunit vaccines?
Considering the principles of vaccine design, what is the most significant advantage of using a recombinant viral vector vaccine that expresses multiple conserved epitopes from a highly variable virus, such as HIV, compared to traditional subunit vaccines?
Given the mechanisms of immunologic memory, what is the most likely outcome of administering a booster dose of a vaccine years after the primary vaccination series?
Given the mechanisms of immunologic memory, what is the most likely outcome of administering a booster dose of a vaccine years after the primary vaccination series?
Within the context of bacterial pathogenesis, what represents the most significant advantage conferred by the formation of biofilms on implanted medical devices?
Within the context of bacterial pathogenesis, what represents the most significant advantage conferred by the formation of biofilms on implanted medical devices?
Considering the intricate balance between immune protection and immunopathology during infection, what represents the most significant risk associated with an excessive or dysregulated type I interferon (IFN-I) response to a viral infection?
Considering the intricate balance between immune protection and immunopathology during infection, what represents the most significant risk associated with an excessive or dysregulated type I interferon (IFN-I) response to a viral infection?
Given the complexities of immune responses in immunodeficient individuals, what is the most likely consequence of a complete deficiency in the recombination activating gene (RAG), preventing V(D)J recombination?
Given the complexities of immune responses in immunodeficient individuals, what is the most likely consequence of a complete deficiency in the recombination activating gene (RAG), preventing V(D)J recombination?
Assessing the role of commensal microbes, what is the MOST ACCURATE statement regarding the impact of broad-spectrum antibiotic use on the human immune system?
Assessing the role of commensal microbes, what is the MOST ACCURATE statement regarding the impact of broad-spectrum antibiotic use on the human immune system?
Considering the role of the thymus, what is the most consequential outcome of a thymectomy performed in early infancy?
Considering the role of the thymus, what is the most consequential outcome of a thymectomy performed in early infancy?
Within the intricate framework of the complement system, what signifies the most consequential advantage conferred by the formation of the membrane attack complex (MAC) on a bacterial cell?
Within the intricate framework of the complement system, what signifies the most consequential advantage conferred by the formation of the membrane attack complex (MAC) on a bacterial cell?
If scientists are engineering novel cytokines, what would be the effect of mutating a cytokine to enhance its receptor-binding affinity while simultaneously reducing its half-life in circulation?
If scientists are engineering novel cytokines, what would be the effect of mutating a cytokine to enhance its receptor-binding affinity while simultaneously reducing its half-life in circulation?
Considering the concept of herd community, what is the most crucial factor that determines the level of vaccine coverage required to achieve herd immunity and protect unvaccinated individuals from a contagious pathogen?
Considering the concept of herd community, what is the most crucial factor that determines the level of vaccine coverage required to achieve herd immunity and protect unvaccinated individuals from a contagious pathogen?
If a new infectious agent is discovered. what cellular mechanism would likely lead to the most devastating outcome of the host's immune system?
If a new infectious agent is discovered. what cellular mechanism would likely lead to the most devastating outcome of the host's immune system?
Following trauma, which event is least likely to occur?
Following trauma, which event is least likely to occur?
What is the least likely microbial defense strategy, given the host challenges?
What is the least likely microbial defense strategy, given the host challenges?
What is the MOST ACCURATE reason the the adaptive immune system is usually recruited when microbes penetrate cellular barriers?
What is the MOST ACCURATE reason the the adaptive immune system is usually recruited when microbes penetrate cellular barriers?
Which statement has the LEAST ACCURATE usage of memory cells?
Which statement has the LEAST ACCURATE usage of memory cells?
With respect to the nature of a barrier, choose the most appropriate option.
With respect to the nature of a barrier, choose the most appropriate option.
With respect to memory properties, choose the most appropriate option.
With respect to memory properties, choose the most appropriate option.
How does the fibrinogen response in the body work?
How does the fibrinogen response in the body work?
What is the MOST ACCURATE impact an immunocompromised patient would experience with respect to memory?
What is the MOST ACCURATE impact an immunocompromised patient would experience with respect to memory?
What is the anticipated affect of cell surface non self indicators trigger?
What is the anticipated affect of cell surface non self indicators trigger?
If a receptor is blocked, what event does this MOST LIKELY impact
If a receptor is blocked, what event does this MOST LIKELY impact
How would you best described the role of IVIG?
How would you best described the role of IVIG?
Between the options, what is the BEST description that summarizes passive immunity?
Between the options, what is the BEST description that summarizes passive immunity?
After a viral infection is cleared, how does active immunization provide?
After a viral infection is cleared, how does active immunization provide?
Why is it important to consider how to respond to an overactive response?
Why is it important to consider how to respond to an overactive response?
Following recognition of an infectious agent by the immune system of a human what would be least expected to occur?
Following recognition of an infectious agent by the immune system of a human what would be least expected to occur?
With respect to the innate and adaptive immune system response to cells, what would be LEAST associated feature with the adaptive immune system?
With respect to the innate and adaptive immune system response to cells, what would be LEAST associated feature with the adaptive immune system?
With respect to adaptive and passive immunity in babies, choose the conclusion that isn't accurate.
With respect to adaptive and passive immunity in babies, choose the conclusion that isn't accurate.
With respect to the nature of the cell surface, what would the effect be of microbes coating surface with host proteins?
With respect to the nature of the cell surface, what would the effect be of microbes coating surface with host proteins?
Given the stochastic nature of V(D)J recombination and junctional diversity in adaptive immunity, what is the MOST COMPLEX problem the body faces in order to leverage an appropriate adaptive immune response?
Given the stochastic nature of V(D)J recombination and junctional diversity in adaptive immunity, what is the MOST COMPLEX problem the body faces in order to leverage an appropriate adaptive immune response?
Within the multifaceted strategies employed by microbes to evade host immune defenses, what is the MOST nuanced implication of a bacterial pathogen's capacity to undergo phase variation, altering the expression of surface-exposed antigens?
Within the multifaceted strategies employed by microbes to evade host immune defenses, what is the MOST nuanced implication of a bacterial pathogen's capacity to undergo phase variation, altering the expression of surface-exposed antigens?
Among the various mechanisms by which the innate immune system discriminates between self and non-self, what represents the MOST critical limitation inherent in the use of pattern recognition receptors (PRRs) that recognize pathogen-associated molecular patterns (PAMPs)?
Among the various mechanisms by which the innate immune system discriminates between self and non-self, what represents the MOST critical limitation inherent in the use of pattern recognition receptors (PRRs) that recognize pathogen-associated molecular patterns (PAMPs)?
Considering the dynamic interplay between the innate and adaptive immune systems, what is the MOST consequential implication of impaired dendritic cell migration from peripheral tissues to secondary lymphoid organs following antigen capture?
Considering the dynamic interplay between the innate and adaptive immune systems, what is the MOST consequential implication of impaired dendritic cell migration from peripheral tissues to secondary lymphoid organs following antigen capture?
Given the complex role of commensal microbes in shaping host immunity, what represents the MOST paradoxical outcome of broad-spectrum antibiotic usage on the development and maintenance of immune homeostasis?
Given the complex role of commensal microbes in shaping host immunity, what represents the MOST paradoxical outcome of broad-spectrum antibiotic usage on the development and maintenance of immune homeostasis?
Flashcards
Human Immune System
Human Immune System
Defensive mechanisms identifying and neutralizing threats to the body.
First Line of Defense
First Line of Defense
Mechanical, chemical, and biologic barriers protecting the body.
Innate Immune System
Innate Immune System
Immune system using fixed receptors encoded in the genome.
Adaptive Immune System
Adaptive Immune System
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Pathogen-Associated Molecular Patterns (PAMPs)
Pathogen-Associated Molecular Patterns (PAMPs)
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Pattern Recognition Receptors (PRRs)
Pattern Recognition Receptors (PRRs)
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V(D)J Recombination
V(D)J Recombination
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Junctional Diversity
Junctional Diversity
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Somatically Generated Receptors
Somatically Generated Receptors
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Immunologic Memory
Immunologic Memory
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Natural Killer (NK) cells
Natural Killer (NK) cells
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MHC Class I Molecules
MHC Class I Molecules
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Microbe
Microbe
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Isolation
Isolation
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Disruption
Disruption
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Ingestion and Consumption
Ingestion and Consumption
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Pattern Recognition Receptors
Pattern Recognition Receptors
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T and B Lymphocytes
T and B Lymphocytes
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Humoral Immunity
Humoral Immunity
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Abscess Formation
Abscess Formation
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Pattern Recognition Receptor
Pattern Recognition Receptor
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Active Immunity
Active Immunity
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Passive Immunity
Passive Immunity
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Natural Immunity
Natural Immunity
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Passive Immunity
Passive Immunity
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Natural/Active Immunity
Natural/Active Immunity
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Acquired and Passive Immunity
Acquired and Passive Immunity
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Acquired and Active Immunity
Acquired and Active Immunity
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Damage-Associated Molecular Pattern molecules (DAMPs)
Damage-Associated Molecular Pattern molecules (DAMPs)
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Overwhelming the Immune System with Tolerance
Overwhelming the Immune System with Tolerance
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Molecular Mimicry
Molecular Mimicry
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Hiding from Immune system
Hiding from Immune system
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Suppressing the Host Immune System
Suppressing the Host Immune System
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Intracellular Evasion
Intracellular Evasion
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Antigenic Variation
Antigenic Variation
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Study Notes
The Need for Self-Recognition
- The human immune system distinguishes "nonself" organisms/molecules (threats) from "self" (body components).
- Threats originate externally (infectious organisms, toxins) or internally (cancerous transformation).
- The immune system has three defense layers: mechanical, chemical, and biological barriers; the innate immune system; and the adaptive immune system.
- The first line of defense consists of mechanical (skin), chemical (stomach acid), and biological (commensal microbes) barriers.
- Commensal microbes are microorganisms living in or on a host without causing harm, often part of the normal microbiota.
- Innate and adaptive immune systems sense threats using cell-surface and soluble receptors, generated differently in each system.
Innate Immune System
- Employs a limited set of receptors encoded in the genome.
- Innate immune receptors recognize Pathogen-Associated Molecular Patterns (PAMPs), common microbial structures absent in human cells.
- Toll-like receptors (TLRs), NOD-like receptors (NLRs), and RIG-I-like receptors (RLRs) exemplify PRRs.
- Provides broad but non-specific pathogen detection due to the limited, unchanging number of receptors.
Adaptive Immune System
- Generates a vast array of B cell (antibodies) and T cell (TCRs) receptors via somatic gene rearrangement.
- V(D)J recombination randomly assembles receptor genes from a pool of segments (Variable, Diversity, Joining).
- Junctional diversity introduces random nucleotide changes during recombination.
- Recognizes virtually any antigen, including those undetectable by the innate immune system.
- Lymphocytes generate unique receptors through gene rearrangement before encountering self or nonself.
- This vetting process retains receptors individualized to recognize that particular self and its nonself environment.
- The initial cellular responses can be modified during subsequent encounters, forming immunologic memory.
- Immunologic memory is a hallmark differentiating the adaptive system from the innate.
Speed vs. Specificity of Immune Systems
- The innate immune system responds rapidly (minutes to hours) but is less specific.
- The adaptive immune system has a slower initial response (days) but offers high specificity and long-term immunity.
- The innate system detects a wide range of microbes using a few conserved pattern receptors.
- The adaptive system can recognize highly specific and novel antigens.
- Innate receptors are evolutionarily conserved, ensuring reliability against common pathogens.
- Adaptive receptors provide evolutionary flexibility, adapting to new or mutating pathogens.
Self vs. Nonself
- Immune cells undergo selection to recognize "self" and consider everything else as "nonself."
- Self-recognition confirms whether encountered molecules or cells belong to the body, ensuring safe interactions.
- Absence of self indicators (e.g., MHC I molecules) can trigger attacks on cells lacking them.
- Natural killer cells use receptors to detect stress signals and assess MHC I levels, killing cells with reduced expression.
- Nonself recognition achieves success through pattern recognition receptors (PRRs) and somatically generated receptors.
- PRRs are genetically stable receptors evolved to recognize structures from distantly related organisms or stressed host cells.
- Lymphocytes' somatically generated receptors are based on genes rearranged within each cell to create a vast, random set.
Pattern Recognition Receptors (PRRs)
- PRRs bind to nonself structures abundant in microbes but not normal host cells.
- They are directly encoded in the genome and expressed identically across individuals.
- PRRs are characteristic of the innate immune system.
- PRRs identify structures associated with microbes, not host cells.
- Some PRRs are on cell membranes (toll-like receptors), while others are soluble (complement system).
Somatically Generated Receptors
- T and B lymphocytes produce somatically generated receptors in the adaptive immune system.
- Each lymphocyte rearranges DNA to develop a unique receptor recognizing a single structure.
- The process leads to a receptor pool recognizing over 10^10 different structures.
- Random receptor generation results in some cells recognizing self, necessitating an "education" process to remove them.
- Lymphocytes that are unable to interact properly are also eliminated.
- Activated T and B lymphocytes launch immune responses to eliminate nonself cells and molecules.
Immunologic Memory
- Innate immune system treats each microbial encounter as novel.
- The adaptive system modifies its responses based on initial encounters, creating immunologic memory.
- Immunologic memory allows tailored responses to frequently encountered cells or molecules.
- Subsequent responses can be rapid and vigorous or depressed against harmless entities, providing context-specific reactions.
Microbes Defined
- Are microscopic organisms, ubiquitous on Earth, and include bacteria, viruses, fungi, protozoa, algae, and archaea.
- Can be neutral (commensal), harmful (pathogens), or beneficial (mutualists).
Defense Mechanisms
- Threats are addressed through isolation, disruption, or ingestion.
- Mechanical, chemical, and biologic barriers prevent microbe entry.
- Invasive microbes may be isolated within structures like granulomas.
- Nonself cells are disrupted via physical damage or apoptosis induction.
- Phagocytic cells ingest microbes and debris, also secreting molecules to activate the immune system.
- Natural killer cells destroy abnormal host cells (e.g., virally infected).
- Antibodies and complement initiate microbe destruction, while T lymphocytes attack microbes and infected cells.
- Immune cells proliferate rapidly to combat threats effectively.
Review Questions Covered
- Natural killer cells assess other cells by detecting MHC class I molecule types and levels.
- Natural killer cells can detect reduced expression and kill those cells from viral infection or becoming cancerous.
- Pattern recognition receptors (PRRs) bind to pathogen-associated molecular patterns (PAMPs).
- Somatically generated receptors on B and T lymphocytes are randomly generated during development.
- Influenza viruses are recognized by the human immune system due to pathogen-associated molecular patterns (PAMPs).
- Initial activation of the immune response to infections results from pattern recognition receptors and coronavirus RNA interactions.
PAMPs and DAMPs
- PAMPs (Pathogen-associated molecular patterns) are microorganisms derived and recognized by pattern recognition receptor (PRR)-bearing cells.
- DAMPs (Damage-associated molecular patterns) are cell-derived, initiating immunity, in response to trauma, ischemia, and tissue damage.
How Microbes Defend Against Host Recognition
- Overwhelm the Immune System with Tolerance (Tolerance: reduced immune response to an antigen due to high persistent doses of antigens).
- Molecular Mimicry (Microbe's antigens look very similar to the host’s own proteins).
- Hiding from the Immune System (coating themselves with host proteins such as fibrin, fibronectin, or even antibodies).
- Suppressing the Host Immune System (Certain microbes directly weaken or suppress the immune system; Viruses, protozoa, and some bacteria can cause immunosuppression).
- Intracellular Evasion (Some pathogens live inside host cells to avoid detection by the immune system).
- Antigenic Variation (periodically change antigens, i.e., to undergo antigenic variation).
Host Defenses
- Innate (nonspecific) immune system provides general protection.
- Includes physical barriers like skin and complement system cells.
- Adaptive immune system offers specific protection.
- B and T cells generate antibodies to tag/destroy invaders.
- Failure of these defenses leads to infection or death.
- AIDS patients with low CD4+ (T helper) cells are prone to bacterial, fungal, and viral infections.
- Intravenous catheters breach skin barriers, increasing the risk of infections.
- The host defense is interconnected and responsive.
- Invading microbes evade physical/chemical defenses (skin, enzymes).
- Microbes survive attacks by macrophages, neutrophils, complement.
- They must also survive attacks by antibodies and cytotoxic T cells.
Humoral Immunity
- Branch of adaptive immunity involves B cells and antibodies.
- Targets extracellular pathogens and toxins.
Abscess Formation
- Abscess means normal tissue, like skin if it's split apart and that new space is invaded by nearby pathogens like bacteria.
- Abscesses are advantageous to bacteria because it is a formation of normal tissue; and roughly ten more bacteria cells are added. Abscesses are a mixture of bacteria, immune cells, and dead tissue. This makes it highly infectious if it gets spread from one place to another.
Self vs Nonself Recognition
- "Self": Cells with the same unique structures as the rest of the body.
- "Nonself": Absence of recognizable structures.
- Receptors act as "lock and key" for recognition. Pattern recognition receptors (PRRs) attach to host cells, recognizing foreign proteins and sending warning signals.
- B and T cells produce somatically generated receptors to unlock specific foreign structures.
Active vs Passive Immunity
- Active Immunity (Antibodies are produced by the body - body is affected was alive or killed by organisms, or toxins we chose barriers). Requires a host pathogen interaction
- Passive community (Antibodies are passed to the body. Mother of passive antibodies to baby through birth, and breast month). Implies preformed antibodies
- Disadvantage of Passive immunity (The duration is temporary).
Immunity Categories
- Natural and Passive means (Infant receives natural/passive immunity from mother.)
- Natural and Active means (Host both acquired the immunity from exposure to the disease organism through infection and the host produced the antibodies to that disease).
- Natural and Acquired means (Host received immunity through the introduction of a vaccine or artificial method, and the host is not producing their own immunity. The immunity is passive and temporary, most often a post-exposure prophylaxis (i.e., administered antivenom)).
- Acquired and Active means (Host received immunity through the introduction of a killed, weakened, biologic form of the disease organism most often through vaccination. Resulting in the host actively producing their own immunity – long lasting immunity (i.e., COVID-19 vaccine)).
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Description
The human immune system distinguishes between 'self' and 'nonself' to identify and neutralize threats. It employs mechanical, chemical, and biological barriers as the first line of defense. The innate immune system uses a limited set of receptors to recognize common microbial structures.
