How does the body protect itself from the invasion of pathogens?

What are pathogens?

bacteria virusesPathogens

fungi protists

“Germs”

International Pathogens

Pathogen - an infectious agent that can cause disease in its host

How does the body defend itself ?

Defense

Offense

First Line of DefenseFirst Line of Defense

Physical BarriersPhysical Barriers

Chemical BarriersChemical Barriers

How does the body prevent How does the body prevent pathogens from entering?pathogens from entering?

Where can pathogens enter the Where can pathogens enter the body?body?

Physical Barriers

Chemical Chemical BarriersBarriers

Second Line Of Defense

Inflammation

What happens if the pathogens get through the first line of

defense?

phagocytosis

phagocytosisphagocytosis

http://www.youtube.com/watch?v=fpOxgAU5fFQ

What happens if the first and second lines of defense are not enough to stop the pathogens?

The Immune Response

The third (and last) line of defense:

Antigen - any substance that is recognized as foreign to the body and stimulates an immune response

Lymphatic systemLymphatic system

Lymphatic System

• absorbs and transports digested fat from the small intestine

villus

• transports lymph - a tissue- cleaning fluid

• transports white blood cells

A Lymph Node

Paul Revere

How is a lymph node like a police How is a lymph node like a police station?station?

Helper T cell

Phagocyte

Receptorr

Antigen

Helper T cell- Sounds the alarm

What does a helper T-cell “say”?

Phagocyte Helper T cell

-Why?

Help!!!The helper T-cell activates the rest of the

immune system

YYY

YY

YY

YY

Y

Y

Y

B Cells

Killer T Cells

Antibodies

Helper T cell

Antibody

B Cell

B cell

B CellMemory B Cell

Antibodies

What does a memory B cell say?

Memory B Cell

NEVER FORGET!!!

What is Immunity?the ability of the body to resist a disease

The Immune ResponseThe Immune Response

The Immune Response

Macrophages engulf, destroy antigen

Macrophage displays antigen to Helper T cell

Helper T cell activated

Helper T cells activate B cells and Killer T cells

Activated B cells and T cells divide; form more B and T cells and memory cells

“Army” of B and T cells attack antigen & infected cells (B cells make antibodies etc…)

Macrophages “clean up” debris

Antigen enters body

Memory cells remain ready JIC…

What is the first line of defense?

What is the second line of defense?

What is the third line of defense?

Physical and chemical barriers

Inflammation

The Immune Response

If you have the chicken pox once why don’t you

(usually) get it again?

Memory B Cell

NEVER FORGET!!!

How is the secondary response different from the primary response?

How is the secondary response How is the secondary response different from the primary response?different from the primary response?

Secondary immune response is stronger, faster, Secondary immune response is stronger, faster, and longer than the primary response.and longer than the primary response.

What is a vaccine?What is a vaccine?A weakened or dead pathogen put into the body to stimulate the production of antibodies and memory cells (immune response)

How is a vaccine like How is a vaccine like sparring?sparring?

How do vaccines protect us from How do vaccines protect us from disease?disease?

Vaccines activate the primary Vaccines activate the primary immune response (stimulate immune response (stimulate the body to produce the body to produce antibodies and memory cells)antibodies and memory cells)

A boy became ill with the chicken pox and recovered. A year later, he was exposed to the same disease again but did not become ill. Why didn’t he develop chicken pox after the second exposure? Explain using the following terms:

primary immune response, secondary

immune response, memory cells, antibodies, antigen

When the boy got infected the first time his primary immune response was activated and he made antibodies to attack the antigen. His immune cells divided and left behind memory cells. When he got infected the second time his memory cells made the secondary immune response fight the disease faster and stronger, so he didn’t even get sick..

Antibody

What is this?

For each kind of pathogen the body makes specific antibodies (and cells of the immune system) that recognize it

Active Immunity Passive Immunity

You make You don’t make

the antibodies the antibodies

Exposure to antigen

- vaccine

- infection

- injection

- breastfeeding

Active immunity

Passive Immunity

1. Antigen enters body

2. Macrophages engulf and destroy antigen or cell infected with antigen

The Immune Response

3. Macrophage displays antigen to helper T cells (activating them)

4. Activated Helper T cell activates B cells and Killer T cells

The Immune Response

5. Activated B cells form memory B cells and plasma cells (which make antibodies)

Activated T cells form memory T cells and killer T cells

The Immune Response

6. Antibodies bind to free antigen and target them for destruction by macrophages

Killer T cells destroy infected cells

The Immune Response

http://www.youtube.com/watch?v=Rpj0emEGShQHow viruses infect cells

http://www.youtube.com/watch?v=U2h0ECyMWhEHIV destroying Helper T cells

The Immune ResponseThe Immune Response

The Immune ResponseThe Immune Response