Innate Immunity Overview

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Questions and Answers

What is the primary role of dendritic cells in the immune system?

Degranulating mast cells

Activating T cells (correct)

Forming epithelial barriers

Secreting antibodies

Which of the following cells is considered a source of cytokines?

Phagocytes

Mast cells (correct)

B lymphocytes

NK cells

What type of immunity involves the production of antibodies?

Passive immunity

Adaptive immunity (correct)

Cell-mediated immunity

Innate immunity

What is the function of epithelial barriers in the immune system?

Preventing pathogen entry Signup and view all the answers

Which immune cells are specifically involved in the innate immune response?

Phagocytes and NK cells Signup and view all the answers

What effect do pro-inflammatory cytokines have on blood vessel tight junctions?

They weaken the tight junctions between cells. Signup and view all the answers

What causes the symptoms of redness and heat during inflammation?

Increased blood vessel diameter and blood flow. Signup and view all the answers

What is the role of bradykinins in tissue during inflammation?

They sensitize nerve endings to cause pain. Signup and view all the answers

How does the innate immune system recognize pathogens?

By recognizing pathogen-associated molecular patterns (PAMPs). Signup and view all the answers

What characteristic do Pattern Recognition Receptors (PRRs) possess?

They can recognize similar shapes on multiple pathogens. Signup and view all the answers

What is the main consequence of increased vascular permeability during inflammation?

Facilitates the infiltration of fluid into surrounding tissues. Signup and view all the answers

What does the inflammatory response indicate about the body’s state?

An active fight against foreign pathogens or damage. Signup and view all the answers

Which cells are primarily responsible for recognizing PAMPs?

Resident immune cells in barrier tissues. Signup and view all the answers

What role does NFκB play in the immune response?

It binds to DNA to instruct cells to produce cytokines. Signup and view all the answers

Which of the following Toll Like Receptors (TLRs) is associated with lipopolysaccharides (LPS)?

TLR 4 Signup and view all the answers

What is the result of recognition of a pathogen by Toll Like Receptors?

Transcription changes leading to cytokine release. Signup and view all the answers

Which relates to the role of cytoplasmic NFκB?

It induces changes to transcription and cytokine release. Signup and view all the answers

What is NOT a ligand for TLR 2?

LPS Signup and view all the answers

Which category do NOD and RIG-like receptors contribute to?

Type I interferon release. Signup and view all the answers

Which cytokine is primarily impacted by the internalization of pathogens?

Interferons Signup and view all the answers

What is a common outcome of the action of Toll Like Receptors?

Internalization and subsequent destruction of the pathogen. Signup and view all the answers

What initiates the activation of complement proteins?

Entry into the tissue Signup and view all the answers

What role do C3a and C5a play in the immune response?

They recruit phagocytic cells. Signup and view all the answers

Which pathway of complement activation is driven by antibodies?

Classical pathway Signup and view all the answers

What is the main function of phagocytes in the immune response?

Destroying pathogens Signup and view all the answers

What does the process of chemotaxis involve?

Recruitment of immune cells to the site of infection Signup and view all the answers

Which complement protein is recognized by phagocytes through their phagocytic receptors?

C3b Signup and view all the answers

What happens as a result of the Membrane Attack Complex formed by complement activation?

Disruption of the cell membrane of pathogens Signup and view all the answers

Which pathway allows for the recognition of mannose on pathogens?

Mannose-binding Lectin pathway Signup and view all the answers

What role do chemokines play in the immune response?

They stimulate migration and activation of cells. Signup and view all the answers

Which cytokines are responsible for up-regulating adhesion molecules on blood vessels during inflammation?

IL-1β and TNF-α Signup and view all the answers

How do neutrophils initially bind to the blood vessel during normal conditions?

By rolling along E-selectin via their proteoglycans. Signup and view all the answers

What happens to neutrophils once they recognize CXCL8?

They start to extravasate into the tissue. Signup and view all the answers

What is the significance of E-selectin during the neutrophil recruitment process?

It allows neutrophils to roll along the vessel surface. Signup and view all the answers

What is CXCL8's role in the recruitment of neutrophils?

It serves as an adhesion factor promoting attachment. Signup and view all the answers

During an infection, what triggers the release of pro-inflammatory cytokines?

Damage to tissues or presence of pathogens. Signup and view all the answers

Which adhesion molecule is involved in the firm attachment of neutrophils after rolling along the blood vessel?

ICAM-1 Signup and view all the answers

What role do chemokines play in neutrophil function?

They attract neutrophils to the site of infection. Signup and view all the answers

Which of the following substances is produced by the formation of NAPDH oxidase?

Superoxide radicals Signup and view all the answers

What is stored in the granules of neutrophils to help combat infections?

Antimicrobial proteins and peptides Signup and view all the answers

What is the result of the respiratory burst performed by neutrophils?

Production of toxic oxygen species Signup and view all the answers

Which complement fragments contribute to the activation of vascular endothelium in neutrophil function?

C5a and C3a Signup and view all the answers

What is NOT a function of neutrophils during an immune response?

Production of antibodies Signup and view all the answers

What type of granules contains myeloperoxidase in neutrophils?

Primary (Azurophilic) granules Signup and view all the answers

What is a key role of defensins found in neutrophil granules?

Disrupting and killing microbial membranes Signup and view all the answers

Study Notes

Innate Immunity

Innate immunity is a body's first line of defence against pathogens
It's a rapid response system
It involves a wide variety of cells and proteins
The cells work together to recognise and eliminate threats
This system is non-specific, meaning it responds to a broad range of pathogens

Immune System

A collection of cells and tissues working to protect against disease
Leukocytes (white blood cells) are produced in bone marrow
Some leukocytes circulate in blood, most reside in tissues/organs

Immune Cells

Monocytes: Precursors to dendritic cells and macrophages
Macrophages: Tissue-resident, phagocytic, antigen-presenting cells
Dendritic Cells: Differentiate in tissues, phagocytic and antigen-presenting. Travel to lymph nodes to activate T cells
Granulocytes:
- Neutrophils: Circulating, highly phagocytic
- Eosinophils: Circulate, respond to IgE, degranulate to remove parasites
- Basophils: Circulating, very low numbers
- Mast Cells: Tissue resident, source of cytokines, can degranulate
Lymphocytes:
- T lymphocytes: Helper and cytotoxic cells, recirculate through lymph nodes, activated by dendritic cells
- B lymphocytes: Produce antibodies
- Natural Killer Cells: Innate immune cells killing infected cells

Physical Barriers

Protect entrances to body
Respiratory tract, skin, gastrointestinal tract, genitourinary tract, and eyes
Tight epithelial layer, fluids, and secretions to protect these entrances

Defenses at Barriers

Tight Epithelial Layers: Restrict movement of materials between cells
Fatty Acids: Destabilise bacterial cell membranes
Defensins: Antimicrobial peptides disrupting cell membranes
Enzymes: e.g., lysozyme in tears, reduce chance for microbial settlement
Normal Microbiota: Outcompete harmful organisms
Low pH: Restricts pathogen survival

Inflammation

A body's response to damage
Characterized by redness (rubor), heat (calor), swelling (tumor), and pain (dolor)
Part of the body's defense mechanisms
Initiated without pathogen presence by cell fragments or other damage

Pro-inflammatory cytokines

Small proteins released by immune cells to communicate
Trigger inflammatory reactions
IL-1β, TNF-α, IL-6: Key pro-inflammatory cytokines released in response to damage

Cytokine Effects on Tissue

Pro-inflammatory cytokines act on endothelial cells to increase permeability
Causes fluid to leak into tissues (edema)
Causes increased blood vessel diameter, resulting in redness and heat
Release of bradykinins sensitizes nerve endings, causing pain

Pathogen Recognition

Pathogen-associated molecular patterns (PAMPs) distinguish pathogen surfaces/nuclear material
Recognized by pattern-recognition receptors (PRRs) on tissue and immune cells

Pattern Recognition Receptors (PRRs)

Same shape on various microbes
Innate immune system, evolved alongside pathogens
Responses are similar for different pathogens

Cell Receptors

External Receptors: (Toll-like Receptors) result in changes to transcription and cytokine release
Cytoplasmic Receptors: (NOD and RIG-like receptors) result in changes to transcription and cytokine release
Endosomal Receptors (Toll-like Receptors) result in changes to transcription and type I interferon release

Toll-Like Receptors (TLRs)

Recognize various pathogen components
Signal transduction activates transcription of pro-inflammatory cytokines

Phagocytic Receptors

Important for engulfing and destroying pathogens
Examples include C-type lectin receptors (e.g., Dectin-1), scavenger receptors, and mannose receptors
Recognize specific pathogen components

Macrophages Killing Pathogens

Pathogens recognized by receptors
Phagocytosis is induced
Phagosome fuses with lysosome
Pathogen broken down and destroyed
Lysosome contains antimicrobial peptides, lysozyme, and nitric oxide

Complement Proteins

Small proteins produced by the liver
Become active when they enter tissues
Binding to pathogen surfaces makes them visible to phagocytic receptors

Chemotaxis

Process of cell recruitment to infection site
Induced by chemokines
Chemokines attract leukocytes to the site of infection

Neutrophil Function

Granules contain antimicrobial proteins and peptides
Produce superoxide radicals
Lower pH and activate peptides within 3 minutes of phagocytosis

Neutrophil Apoptosis and Netosis

Respiratory burst produces toxic oxygen species
Eventually, neutrophils die (apoptosis or netosis)
During netosis, chromatin and granule contents are released (Neutrophil Extracellular Traps (NETs))

Systemic Effects of Pro-inflammatory Cytokines

Liver: Induces acute phase protein production
Fat and Muscle: Protein and energy mobilization, increased body temperature
Hypothalamus: Increases body temperature
Bone Marrow & Epithelium: Neutrophil mobilization

Incomplete Pathogen Clearance

Continued cytokine release can damage tissues
Damaged blood vessels and bradykinin release contribute to pain and swelling

Summary

Barriers try to prevent injury or infection
If breached, damage/pathogens induce inflammation
Cytokines have local and systemic effects to enhance immune responses
Tissue resident cells, like macrophages, act early to phagocytose pathogens; neutrophils are recruited

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Description

Explore the vital role of innate immunity as the body’s first line of defense against pathogens. This quiz covers the characteristics of immune cells, their functions, and how they work together to eliminate threats efficiently. Ideal for students studying immunology or biological sciences.