1. How do your cells fight off invaders?
Immune response
How do your cells fight off invaders?

2. Introduction
You do not get sick every time disease causing germs enter your body. Sometimes white blood cells attack and destroy invaders without your feeling ill. Other times, you get sick because germs start winning. Fortunately, a healthy immune system can overpower many different types of germs – even when germs temporarily gain the upper hand.

3. Pathogen A disease causing agent Types of Pathogens:
Bacteria
Viruses
Others: Fungi (athlete’s foot), Protists (Malaria) & Parasites (heart worm)
They cause disease by destroying cells, releasing toxins and/or disrupting body functions

4. How do pathogens enter the body?
Direct Contact
Requires an infected person or animal to have physical contact (blood/bodily fluids) with a healthy person (Ex. Rabies or HIV)
Indirect Contact
Pathogens surviving on non-living surfaces (tables, door knobs, etc.)
Air – coughing & sneezing
Vectors
Anything that carries a pathogen & transmits it to healthy cells (mosquitoes)

5. Draw the Following in your notes:
Bacteria
Virus
Size
(Compared to each other)
Shape
Living or Non-living
# of Cells
Reproduction
DNA & RNA?
Treatment
Can it be beneficial?
Examples

6. (compared to each other)
Bacteria
Virus
Size
(compared to each other)
Huge compared to viruses
Sub-microscopic particles (tiny compared to bacteria)
Shape
Spheres, rods or spiral
Microscopic particle
Living or Non-living
Living
Non-living (although it’s debated – they do not meet all of the criteria of living things)
# of Cells
Unicellular
None – not living
Reproduction
Fission – a form of asexual reproduction
Cannot reproduce on their own. They replicate by infecting a host cell.

7. Bacteria Virus How is it treated? Can it be beneficial? Examples
Bacteria
Virus
DNA & RNA?
Yes
DNA or RNA (enclosed in a protein coat). Can mutate & evolve.
How is it treated?
Antibiotics
“Let nature take its course”
Vaccines are preventative
Can it be beneficial?
Yes (used to make cheese & yogurt!) No
Examples
Strep throat, E.Coli, food poisoning
Flu, colds, AIDS

8. How do we control Pathogens?

9. Antibiotics
Medicines that target bacteria & fungi and keep them from growing & reproducing
Can ONLY be used for bacterial and fungal infections!!!
Antibiotic resistance occurs when bacteria mutate so they are no longer affected by antibiotics

10. Vaccines
A killed or weakened form of a pathogen that is injected into your body which causes it to build an immunity to that type of virus

12. What is the Function of the immune system?
To fight off infection & pathogens
Antigen – any substance that causes your body to produce antibodies (proteins) against the invader
Antigens trigger a response by your immune system
Pathogens can also be antigens
Two lines of defense…

13. Non-specific Defenses *They react the same to all pathogens
Also called passive defenses
Skin – forms a barrier that few pathogens can get through
Inflammation – swelling
Mucus, saliva & tears – trap pathogens and contain enzymes that kill bacteria
Fever – higher body temp slows the growth of many pathogens

14. Specific Defenses *Different for every pathogen
Also called active defenses
White blood cells (B cells & T cells)
Travel through the blood stream & attack pathogens
Example: Phagocyte (type of white blood cell that destroys pathogens by surrounding and engulfing them)

15. Specific defenses cont’d
Antibodies (proteins)
Some cause pathogens to clump making them easier to engulf
Some track down and destroy infected cells
Some called memory cells, will remain in the body so if that pathogen appears again, they will quickly respond