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What is the primary function of the innate immune system?
What is the primary function of the innate immune system?
- To produce antibodies against specific antigens
- To differentiate between self and non-self antigens
- To prevent the entry of pathogens into the host (correct)
- To recognize and kill infected cells
Which of the following is NOT a characteristic of the innate immune system?
Which of the following is NOT a characteristic of the innate immune system?
- It responds differently to each pathogen (correct)
- It uses a limited set of molecules to recognize infection
- It is present at birth
- It directs the acquired immune response
What is the role of phagocytes in the innate immune system?
What is the role of phagocytes in the innate immune system?
- To differentiate between self and non-self antigens
- To engulf and digest foreign particles and bacteria (correct)
- To recognize and neutralize viral particles
- To produce cytokines that activate T cells
What is the primary function of the complement system in the innate immune system?
What is the primary function of the complement system in the innate immune system?
Which of the following is an example of a physical barrier in the innate immune system?
Which of the following is an example of a physical barrier in the innate immune system?
What is the time frame for the activation of the innate immune system?
What is the time frame for the activation of the innate immune system?
Which of the following is NOT a type of cellular component in the innate immune system?
Which of the following is NOT a type of cellular component in the innate immune system?
What is the relationship between the innate and adaptive immune systems?
What is the relationship between the innate and adaptive immune systems?
What is the primary function of collectins in the innate immune response?
What is the primary function of collectins in the innate immune response?
What is the term for the molecular structures present in many different microorganisms that are recognized by the innate immune response?
What is the term for the molecular structures present in many different microorganisms that are recognized by the innate immune response?
What is the primary function of Toll-like receptors in the innate immune response?
What is the primary function of Toll-like receptors in the innate immune response?
What is the term for the first line of defense against pathogens, which includes physical barriers such as the skin and mucous membranes?
What is the term for the first line of defense against pathogens, which includes physical barriers such as the skin and mucous membranes?
What is the term for the type of immunity that is present from birth and provides immediate defense against pathogens?
What is the term for the type of immunity that is present from birth and provides immediate defense against pathogens?
What is the term for the process by which the innate immune response recognizes and responds to pathogens?
What is the term for the process by which the innate immune response recognizes and responds to pathogens?
Which Toll-like receptor is specifically responsible for recognizing lipopeptides from Gram-positive bacteria?
Which Toll-like receptor is specifically responsible for recognizing lipopeptides from Gram-positive bacteria?
What type of molecule does NOD2 specifically sense in the immune response?
What type of molecule does NOD2 specifically sense in the immune response?
Which Toll-like receptor is primarily engaged in the recognition of dsRNA viruses?
Which Toll-like receptor is primarily engaged in the recognition of dsRNA viruses?
What is the primary function of the complement system in the innate immune response?
What is the primary function of the complement system in the innate immune response?
Which receptor among the Toll-like receptors is responsible for recognizing Gram-negative bacteria through LPS?
Which receptor among the Toll-like receptors is responsible for recognizing Gram-negative bacteria through LPS?
Which of the following is NOT an effector mechanism of the innate immune response?
Which of the following is NOT an effector mechanism of the innate immune response?
What role do TLRs play in the immune system?
What role do TLRs play in the immune system?
Which Toll-like receptor is associated with the recognition of single-stranded RNA viruses?
Which Toll-like receptor is associated with the recognition of single-stranded RNA viruses?
Which of the following pathways is primarily responsible for the activation of the complement system when an antibody binds to an antigen?
Which of the following pathways is primarily responsible for the activation of the complement system when an antibody binds to an antigen?
What is the role of the C3 convertase in the complement system?
What is the role of the C3 convertase in the complement system?
Which of the following is NOT a direct effect of the membrane attack complex (MAC) formed during the complement cascade?
Which of the following is NOT a direct effect of the membrane attack complex (MAC) formed during the complement cascade?
What is the primary difference between macrophages and neutrophils in terms of their lifespan and location?
What is the primary difference between macrophages and neutrophils in terms of their lifespan and location?
Which of the following is NOT a mechanism used by macrophages and neutrophils to kill pathogens?
Which of the following is NOT a mechanism used by macrophages and neutrophils to kill pathogens?
What is the role of cytokines in the innate immune response?
What is the role of cytokines in the innate immune response?
Which of the following is NOT a major cytokine involved in the innate immune response?
Which of the following is NOT a major cytokine involved in the innate immune response?
What is the primary function of chemokines in the immune response?
What is the primary function of chemokines in the immune response?
Which of the following is the best description of the role of the skin in the innate immune system?
Which of the following is the best description of the role of the skin in the innate immune system?
What is the role of the enzyme inducible nitric oxide synthase (iNOS) in the immune response?
What is the role of the enzyme inducible nitric oxide synthase (iNOS) in the immune response?
Which cytokine plays a critical role in activating macrophages and upregulating MHC molecules?
Which cytokine plays a critical role in activating macrophages and upregulating MHC molecules?
What are the primary cells involved in early antigen presentation to activate T cells?
What are the primary cells involved in early antigen presentation to activate T cells?
Which of the following signals is required for T cell activation along with MHC interaction?
Which of the following signals is required for T cell activation along with MHC interaction?
Which type of interferons are primarily produced in response to viral infections?
Which type of interferons are primarily produced in response to viral infections?
What process do Dendritic cells undergo to enhance their ability to present antigens?
What process do Dendritic cells undergo to enhance their ability to present antigens?
Which immune response is characterized by the recognition of pathogens through pattern recognition receptors (PRRs)?
Which immune response is characterized by the recognition of pathogens through pattern recognition receptors (PRRs)?
What is the duration of the induced immune response before acquired immunity takes over?
What is the duration of the induced immune response before acquired immunity takes over?
Which of the following best describes the role of cytokines in the immune response?
Which of the following best describes the role of cytokines in the immune response?
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Study Notes
Innate Immunity
- Innate immunity is a non-specific defense mechanism that a host uses immediately or within several hours after exposure to an antigen.
- Characteristics of the innate immune system:
- Designed to be very fast, responding within hours
- Ancient evolution, with components found in invertebrates such as amoebae, snails, and fruit flies
- Responds exactly the same way each time
- Uses a handful of molecules to recognize infection
- Induces and directs the acquired/adaptive immune response
Components of the Innate Immune System
- Physical/anatomical barriers:
- Skin
- GI tract
- Respiratory tract
- Mucosal epithelia
- Secreted compounds:
- Antibacterial compounds
- Complement
- Natural antibodies
- Cytokines
- Cellular components:
- Phagocytes
- NK cells
Goals of the Innate Immune Response
- Prevent entry of the pathogen:
- Physical barrier protection: skin, GI tract, and respiratory tract
- Mechanical and secreted protection: peristalsis, hydrochloric acid production, and low pH
- Internal protection: microbial competition
- Recognise the pathogen:
- Recognise a few highly conserved molecular structures present in many different microorganisms
- Pathogen-associated molecular patterns (PAMPs)
Pattern Recognition Receptors (PRRs)
- Collectins:
- Family of proteins present in solution
- Collagen-like region and a lectin region
- Interact with effector parts of the immune system
- Bind to sugar molecules on the surface of pathogens
- Toll-like receptors (TLRs):
- At least 10 mammalian homologues
- Recognise Gram-negative bacteria (LPS) and Gram-positive bacteria (peptidoglycan, lipopeptide)
- Recognise Mycoplasma (lipopeptide) and RNA virus (dsRNA, polyl:C)
- NOD-like receptors (NLRs):
- Sense g-glutamyl diaminopimelic acid (NOD1) and Muramyl dipeptide (NOD2)
Effector Mechanisms of the Innate Immune Response
- Complement:
- Series of proteins that circulate in blood and tissue fluids
- Operates via a cascade (one product induces the formation of the next)
- Phagocytosis and killing:
- Monocyte/macrophage and neutrophil
- Recognition of the pathogen by receptors on the phagocyte leads to ingestion and destruction
- Cytokines:
- Proteins that bind to specific receptors
- Can be activating or deactivating
- Mainly activating in the innate immune response (IL-1, IL-6, TNFα)
- Activation of adaptive immunity
Phagocytosis and Killing
- Recognition of the pathogen by receptors on the phagocyte leads to ingestion and destruction
- Killing mechanisms:
- Reactive oxygen intermediates (more in neutrophils)
- Reactive nitrogen intermediates (more in macrophages)
Cytokines and Chemokines
- Proteins that bind to specific receptors
- Can be activating or deactivating
- Mainly activating in the innate immune response (IL-1, IL-6, TNFα)
- Chemokines:
- Class of cytokines with chemoattractant properties
- Promote inflammation by enabling cells to adhere to the surface of blood vessels and migrate to infected tissue
Interferons
- Type 1 interferons (IFNα and IFNβ):
- Produced in response to virally infected cells
- Natural killer cells responsive to TNFα, IL-12
- Produce IFNγ
- IFNγ:
- Critical cytokine that activates macrophages
- Upregulates MHC molecules
- Together with IL-12, stimulates differentiation of CD4 Th1 cells
Innate Immunity to Adaptive Immune Response
- Antigen presenting cell:
- Presents antigen to activate T cells
- MHC, TCR, and co-stimulation
- Signal 1:
- Antigen presentation
- Signal 2:
- Co-stimulation
- Cytokines (IL-12, IL-6, TNFα)
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