chapter 21: the immune system (#1)

CHAPTER 21: THE IMMUNE

SYSTEM (1): INNATE

IMMUNITY

Human Anatomy and Physiology II –

BIOL153

Goals/Objectives

Explain the key differences between the innate vsadaptive immune system

Describe surface membrane barriers and their protective functions

Explain the importance of phagocytosis and natural killer cells in innate body defense

Name the body’s antimicrobial substances and describe their functions

Describe the inflammatory process. Identify the cardinal signs of acute inflammation and indicate their causes

Explain how fever helps the body

Immunity

Immune System – Innate vs

Adaptive

Innate:

• Nonspecific

• Responds

quickly

Adaptive:

• Specific

• Responds

Slowly the

1st time

Immunity

Innate

ImmunityAdaptive

Immunity

Immunity

Innate

Defenses

(Wed)

Surface barriers (1st

line)

• Skin• Mucous membranes

Internal defenses (2nd

line)

• Phagocytes• Natural killer cells• Inflammation• Antimicrobial proteins• Fever

Adaptive

Defenses

(Fri)

Humoral immunity

• B cells

Cellular immunity

• T cells

Innate Defenses

Surface barriers ward off invading pathogens –

first line of defense

Skin, mucous membranes, and their secretions

Innate Defenses

Internal Defenses: Cells and Chemicals

Necessary if microorganisms invade deeper

tissues – Second Line of Defense

Phagocytes

Neutrophils most abundant but die fighting

Become phagocytic on exposure to infectious material

Macrophages develop from monocytes – chief phagocytic cells – robust cells

Free macrophages wander through tissue spaces, e.g., alveolar macrophages

Fixed macrophages permanent residents of some organs; e.g., stellate macrophages (liver) and microglia (brain)

© 2013 Pearson Education, Inc.

Phagocyte adheres to pathogens or debris.

1

Lysosome

Events of phagocytosis.



1

Phagocyte forms pseudopods that eventually engulf the particles, forming a phagosome.

2

Phagosome(phagocyticvesicle)

Lysosome




1


Lysosome fuses with the phagocytic vesicle, forming a phagolysosome.

2

3


Lysosome

Acidhydrolaseenzymes




1



Lysosomal enzymes digest the particles, leaving a residual body.

2

3

4


Lysosome





1



Lysosomal enzymes digest the particles, leaving a residual body.

Exocytosis of the vesicle removes indigestible and residual material.

2

3

4

5


Lysosome



Natural Killer (NK) Cells

Antimicrobial Proteins

Some attack microorganisms directly

(compliment)

Some hinder microorganisms' ability to

reproduce/survive

Include interferons and complement proteins

Interferons

Family of immune modulating proteins

Viruses lack the essential cellular machinery to generate ATP or synthesize protein

They cannot reproduce themselves

They hijack other cells to do their work

Viral-infected cells secrete IFNs (e.g., IFN alpha and beta) to "warn" neighboring cells

IFNs enter neighboring cells produce proteins that block viral reproduction and degrade viral RNA

IFN alpha and beta also activate NK cells


Innate defenses Internal defenses

VirusViral nucleic acid

Virus enters cell.1

Host cell 1

Host cell 2

Infected by virus;makes interferon;is killed by virus

Binds interferonfrom cell 1; interferoninduces synthesis ofprotective proteins

Nucleus




Interferon genes switchon.

DNA

Nucleus

Host cell 1

Host cell 2



Virus enters cell.1

2





DNA

Nucleus

mRNA forinterferon

Cell produces interferon molecules. Interferon

Host cell 1

Host cell 2



Virus enters cell.1

2

3





DNA

Nucleus

mRNA forinterferon


Host cell 1

Host cell 2



Virus enters cell.1

2

3

Interferon binding stimulates cell toturn on genes for antiviral proteins.

4




New viruses

Antiviral proteinsblock viralreproduction.


DNA

AntiviralmRNA

Nucleus

mRNA forinterferon


Interferonreceptor

Host cell 1

Host cell 2



Virus enters cell.

5

Interferon binding stimulates cell toturn on genes for antiviral proteins.

4

1

2

3

Complement System

(Complement)

~20 blood proteins that circulate in inactive

form• Called complement

because it helps other

immune cells to

perform their

functions

• Activation unleashes

inflammatory

chemicals that

amplify virtually all

aspects of the

inflammatory

process

• It can also lyse and

kill certain bacteria

and other cell types.

Complement

Clicker Question

Which of the following is not a mechanical

barrier to pathogen invasion?

a) Mucus membranes

b) Complement

c) Skin

d) Saliva

Goals/Objectives

Explain the key differences between the innate vsadaptive immune system

Describe surface membrane barriers and their protective functions

Explain the importance of phagocytosis and natural killer cells in innate body defense

Name the body’s antimicrobial substances and describe their functions

Describe the inflammatory process. Identify the cardinal signs of acute inflammation and indicate their causes

Explain how fever helps the body

Inflammatory Response (functions in

bold)

Triggered whenever body tissues

injured

Prevents spread of damaging

agents

Disposes of cell debris and

pathogens

Alerts adaptive immune system

Inflammatory Response

Cardinal signs of acute inflammation:

1. Redness

2. Heat

3. Swelling

4. Pain

(Sometimes 5. Impairment of function)


Initial stimulus

Physiological response

Signs of inflammation

Result

Arterioles

dilate

Local hyperemia(increased blood

flow to area)

Heat Redness

Release of inflammatory chemicals(histamine, complement,

kinins, prostaglandins, etc.)

Increased capillary

permeability

Capillariesleak fluid

(exudate formation)

Leaked protein-richfluid in tissue spaces

Pain Swelling

Possible temporary

impairment of

function

Locally increasedtemperature increasesmetabolic rate of cells

Tissue injury

Attract neutrophils,monocytes, andlymphocytes to

area (chemotaxis)

Leaked clottingproteins form interstitialclots that wall off area

to prevent injury tosurrounding tissue

Temporary fibrinpatch forms

scaffolding for repair

Healing

Release of leukocytosis-

inducing factor

Leukocytosis (increased numbers of whiteblood cells in bloodstream)

Leukocytes migrate to

injured area

Margination (leukocytes cling to

capillary walls)

Diapedesis (leukocytes pass through

capillary walls)

Phagocytosis of pathogensand dead tissue cells

(by neutrophils, short-term;by macrophages, long-term)

Pus may form

Area cleared of debris

Phagocyte Mobilization

Steps for phagocyte mobilization

1. Leukocytosis: release of neutrophils from bone marrow in response to leukocytosis-inducing factors from injured cells

2. Margination: neutrophils cling to walls of capillaries in inflamed area in response to CAMs

3. Diapedesis of neutrophils

4. Chemotaxis: inflammatory chemicals (chemotactic agent) promote positive chemotaxis of neutrophils


Inflammatorychemicals diffusing from the inflamed site act aschemotactic agents.

1

Capillary wall

BasementmembraneEndothelium

Leukocytosis.

Neutrophils enter blood from bone marrow.



Leukocytosis.


Margination.

Neutrophils clingto capillary wall.

1 2

Capillary wall




Leukocytosis.


Margination.


Diapedesis.

Neutrophils flattenand squeeze out of capillaries.

1 2 3

Capillary wall




Leukocytosis.


Margination.


Diapedesis.

Neutrophils flattenand squeeze out of capillaries.

1 2 3

Chemotaxis.

Neutrophils follow chemical trail.

Capillary wall


4

Clicker Question

The process by which phagocytes exit the

capillary and enter injured tissue is called

_________.

a) chemotaxis

b) leukocytosis

c) margination

d) diapedesis

Fever

Abnormally high body temperature

Systemic response to invading microorganisms (not localized)

Leukocytes and macrophages exposed to foreign substances secrete pyrogens

Pyrogens act on body's thermostat in hypothalamus, raising body temperature

Benefits of moderate fever

Causes liver and spleen to sequester iron and zinc (needed by microorganisms)

Increases metabolic rate faster repair

Clicker Question

A person with an upper respiratory infection asks you why a fever occurs with this type of infection. You are aware that the cells of the immune system release chemical agents that enhance the inflammatory response and increase temperature. These are known as:

a) Antigens

b) Antibodies

c) Pyrogens

d) Phagocytes

chapter 21: the immune system (#1)

Education

pathogens fever

innate body defensename

reflexes2nd line of

etc3rd line of defense

invading pathogens

epithelial cells

line of defenseskin

adaptive specific t