1. Fighting Diseases

2. Causes of Disease
Pathogens enter the body and either damage tissues or produce substances that are toxic to the body
The body recognizes pathogens as foreign invaders due to antigens
Antigens are molecules on the surface of pathogens that the immune system recognizes
The body combats disease through the immune system

3. The Immune-System Response
The human body has three main lines of defense:
External barriers (non-specific)
Inflammatory response (non-specific)
Specific Immune Response

4. 1st Line of Defense External Barriers (non-specific)
External barriers are non-specific, meaning they will work to keep out all foreign invaders
The human skin, if unbroken, forms an almost impenetrable barrier against microorganisms
Cells in the nasal passages and pharynx secrete sticky mucus that traps microorganisms and digestive enzymes in the mucus can destroy most microorganisms
The stomach also contains strong acid and enzymes that can kill pathogens

5. 2nd Line of Defense: Inflammatory Response
The 2nd line of defense is also non-specific or innate.
This means it will respond the same to any antigen
This is the defense system you were born with!

6. 2nd Line of Defense Inflammatory Response
Inflammatory response occurs when tissues are injured by bacteria, toxins, trauma, heat, or other things.
The damaged cells release chemicals such as histamine. These chemicals cause blood vessels to leak fluid into the tissues, causing swelling which helps isolate the foreign substance from further contact with body tissues.
The chemicals also attract white blood cells called phagocytes that "eat" germs and dead or damaged cells. This process is called phagocytosis.

7. Inflammatory Response

8. Inflammatory response symptoms
The affected area becomes red, swollen, and warm.
The inflammatory response may also cause a general fever. The increase in body temperature helps fight off the pathogen!

9. 3rd Line of Defense Specific Immune Response
The cells of the immune system are able to distinguish between different kinds of pathogens. The immune system cells then react to each kind of pathogen with a defense that target specifically at that pathogen.
White blood cells that target specific pathogens are called lymphocytes.
B lymphocytes
(B cell)
T lymphocyte
(helper T cell)
antigen

10. Lymphocytes There are two major types of Lymphocyte:
T-cells: Identify pathogens by their antigens
B-cells: produce chemicals called antibodies
Antibodies bind to the antigens on a pathogen, inactivate the pathogen, and mark them for destruction by other immune cells.
Each kind of B-cell produces an antibody that bind to only one kind of antigen

11. Lymphatic system
The lymphatic system is an extensive drainage network that helps keep bodily fluid levels in balance and defends the body against infections.
Lymph nodes help filter out foreign materials and store lymphocytes (white blood cells)

12. Active Immunity vs. Passive Immunity
- Occurs naturally when the body itself manufactures antibodies through fighting off a disease - Occurs artificially when induced by a vaccine. - Provides lasting protection
Passive immunity
- Antibodies are introduced into bloodstream of an individual, given from mother to child during pregnancy and breast-feeding - Provides only short-term protection

13. Prevention of Disease Summary
Proper sterilization and/or cleaning of instruments & surfaces
disinfectants (chemical that kill microorganisms on surfaces) E.g., bleach
Proper use of antiseptics (chemicals that can be used on the skin)
e.g. mouthwash, antibacterial soap
Proper use of antibacterial medication
Vaccinations (dead form of pathogen)
Natural human immune response

14. Aseptic Techniques
A procedure that is performed under sterile conditions
What examples can you think of? In Hospitals? At home? At school?

15. Let’s see this all in action
The Immune Response
Why is it necessary to have so many different types of cells in the immune system?