1. Immune System
Chapter 40-2

2. Immune System
A series of defenses that guard your body against disease
Function: to fight infection by producing cells that inactivate foreign substances or cells
This is called IMMUNITY
Pathogen: disease causing agents such as bacteria, virus, and fungi
Recognizes, attacks, destroys, & “remembers” each type of pathogen that enters the body
Produces specialized cells that inactivate the pathogen

3. Organs of the Immune System

4. Nonspecific Defenses
Do not discriminate between 1 threat and another (reacts the same no matter what)
Include physical & chemical barriers
1st Line of Defense:
1. Most important – SKIN
2. mucus, saliva, tears, oil & sweat glands
2nd Line of Defense: inflammatory response

5. Skin
Very few pathogens can get across the layers of dead cells on the surface
When broken (cuts or wounds), pathogens enter very easily & multiply
Causes symptoms of INFECTION:
1. swelling
2. redness
3. pain
4. heat

6. Secretions of the Body
Mucus, saliva and tears - all contain LYSOZYME – enzymes that breaks down the cell walls of bacteria
Oil & sweat glands produce an acidic environment on the skin that kills many bacteria
Mucus in mouth & nose help trap pathogens
Stomach acids & digestive enzymes destroy many pathogens that get in your stomach

7. Inflammatory Response
A nonspecific defense reaction to tissue damage caused by injury or infection
Millions of white blood cells are produced – which fight the infection
Blood vessels near the wound expand, allowing the WBCs to travel faster to infected tissue
WBCs engulf & destroy bacteria
Area becomes swollen & painful
Body release chemicals to increase body temp. – fever – slows or stops the growth of the pathogen
Fever also causes heart rate to increase which pushes WBCs to infected tissue faster

8. White blood cell vs. Red blood cell

9. Interferons Proteins that help other cells resist viral infections
Interfere with the growth of the virus
Slows down the progress of the infection & gives the immune system time to respond

10. Specific Defenses
If a pathogen gets through the nonspecific defenses, the body STARTS the IMMUNE RESPONSE
ANTIGENS: substances that trigger this response – viruses, bacteria
Cells in the immune system can recognize these antigens are called - lymphocytes

11. Lymphoctyes
B Cells – provide immunity against antigens & pathogens in body fluids
- this is called HUMORAL IMMUNITY
T-cells – provide defense against abnormal cells & pathogens inside living cells.
- this is called CELL-MEDIATED IMMUNITY

12. Humoral Immunity
When a pathogen enters the body, it is recognized by a small amount of B cells
These B cells grow & divide rapidly – producing many memory B cells & Plasma cells

13. Plasma cells
Plasma cells release ANTIBODIES – recognize & bind to antigens
Antibodies attack the pathogen until it has taken it over
Once infection is gone, the plasma cells die & stop producing antibodies

14. Memory B Cells Remember every pathogen that enters the body
Able to produce antibodies if exposed again
Greatly reduces the chance of being infected again

15. Antibody Structure
Shaped like a Y and has 2 binding sites to connect with antigens
The different shapes give antibodies the ability to recognize a large variety of antigens
Its estimated that a healthy adult can produce about 100 million different types of antibodies

16. Antigen-binding sites
Antibody

17. Cell-Mediated Immunity
The body’s primary defense against its own cells when they have become cancerous or infected by viruses
Also important in fighting infection by fungi & protists
Viruses & other pathogens can not be destroyed by antibodies alone

18. Process of cell mediated immunity
T cells divide & change into Killer T cells, Helper T cells, & Memory T cells
Killer T cells find & destroy the pathogen or foreign tissue that contains the antigen
Helper T cells produce Memory T cells
Memory T cells remember the antigen in case of future invasion
Once pathogen is taken over, Suppressor T cells shut down Killer T cells

19. HIV – Human Immunodeficiency Virus

20. Acquired Immunity
when immunity is taken from outside the body – not naturally made
Two types
Active Immunity
Passive Immunity

21. Active Immunity
Vaccination – injection of a weakened form of a pathogen to produce immunity
More than 20 serious human diseases can be prevented by vaccinations
Modern vaccines stimulate the immune system to create millions of plasma cells ready to produce specific types of antibodies
When the body reacts to the vaccines it is known as Active Immunity

22. Passive Immunity
When antibodies produced by other animals against a pathogen are injected into the bloodstream
Last only a short time
Can develop naturally - passing from mother to child through placenta or breast feeing
or by deliberate exposure - vaccines for malaria or when someone is bitten from snake or rodent