Innate Immune Protection Mechanisms

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Questions and Answers

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?

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?

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?

To mark pathogens for destruction by phagocytes Signup and view all the answers

Which of the following is an example of a physical barrier in the innate immune system?

Skin Signup and view all the answers

What is the time frame for the activation of the innate immune system?

Within hours to days Signup and view all the answers

Which of the following is NOT a type of cellular component in the innate immune system?

B cells Signup and view all the answers

What is the relationship between the innate and adaptive immune systems?

The innate immune system induces and directs the adaptive immune response Signup and view all the answers

What is the primary function of collectins in the innate immune response?

To interact with the effector parts of the immune system Signup and view all the answers

What is the term for the molecular structures present in many different microorganisms that are recognized by the innate immune response?

Pathogen-associated molecular patterns Signup and view all the answers

What is the primary function of Toll-like receptors in the innate immune response?

To recognize PAMPs on the membrane Signup and view all the answers

What is the term for the first line of defense against pathogens, which includes physical barriers such as the skin and mucous membranes?

Physical barrier protection Signup and view all the answers

What is the term for the type of immunity that is present from birth and provides immediate defense against pathogens?

Innate immunity Signup and view all the answers

What is the term for the process by which the innate immune response recognizes and responds to pathogens?

Pattern recognition Signup and view all the answers

Which Toll-like receptor is specifically responsible for recognizing lipopeptides from Gram-positive bacteria?

TLR2 Signup and view all the answers

What type of molecule does NOD2 specifically sense in the immune response?

Muramyl dipeptide Signup and view all the answers

Which Toll-like receptor is primarily engaged in the recognition of dsRNA viruses?

TLR3 Signup and view all the answers

What is the primary function of the complement system in the innate immune response?

To circulate as a cascade of proteins Signup and view all the answers

Which receptor among the Toll-like receptors is responsible for recognizing Gram-negative bacteria through LPS?

TLR4 Signup and view all the answers

Which of the following is NOT an effector mechanism of the innate immune response?

Antigen presentation Signup and view all the answers

What role do TLRs play in the immune system?

Recognizing pathogen-associated molecular patterns Signup and view all the answers

Which Toll-like receptor is associated with the recognition of single-stranded RNA viruses?

TLR7 Signup and view all the answers

Which of the following pathways is primarily responsible for the activation of the complement system when an antibody binds to an antigen?

Classical pathway Signup and view all the answers

What is the role of the C3 convertase in the complement system?

Cleaving C3 into C3a and C3b, initiating the cascade Signup and view all the answers

Which of the following is NOT a direct effect of the membrane attack complex (MAC) formed during the complement cascade?

Recruitment of phagocytes Signup and view all the answers

What is the primary difference between macrophages and neutrophils in terms of their lifespan and location?

Macrophages are long-lived and found in tissues, while neutrophils are short-lived and found in blood. Signup and view all the answers

Which of the following is NOT a mechanism used by macrophages and neutrophils to kill pathogens?

Production of antibodies Signup and view all the answers

What is the role of cytokines in the innate immune response?

Acting as intercellular messengers to activate and coordinate immune cells Signup and view all the answers

Which of the following is NOT a major cytokine involved in the innate immune response?

IFNγ (Interferon γ) Signup and view all the answers

What is the primary function of chemokines in the immune response?

Recruiting immune cells to sites of infection Signup and view all the answers

Which of the following is the best description of the role of the skin in the innate immune system?

Acting as a physical barrier to pathogen entry Signup and view all the answers

What is the role of the enzyme inducible nitric oxide synthase (iNOS) in the immune response?

Synthesizing nitric oxide radicals to damage pathogens Signup and view all the answers

Which cytokine plays a critical role in activating macrophages and upregulating MHC molecules?

IFNg Signup and view all the answers

What are the primary cells involved in early antigen presentation to activate T cells?

Macrophages and Dendritic cells Signup and view all the answers

Which of the following signals is required for T cell activation along with MHC interaction?

Co-stimulation via CD28 Signup and view all the answers

Which type of interferons are primarily produced in response to viral infections?

Type 1 interferons Signup and view all the answers

What process do Dendritic cells undergo to enhance their ability to present antigens?

Maturation Signup and view all the answers

Which immune response is characterized by the recognition of pathogens through pattern recognition receptors (PRRs)?

Innate immunity Signup and view all the answers

What is the duration of the induced immune response before acquired immunity takes over?

4-96 hours Signup and view all the answers

Which of the following best describes the role of cytokines in the immune response?

They provide signals for inflammation and recruitment of immune cells. Signup and view all the answers

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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Description

This quiz covers the basics of innate immunity, including epithelial barriers, phagocytes, and the complement system. It is designed to test your understanding of the immune system's first line of defense.