1. The Human Immune System
Video

2. What is immunity?
How our body protects us from pathogens, parasites, and foreign substances.
What is a pathogen?
Any substance that can cause illness (ex: germs, bacteria, viruses, parasites)
Our body has two main types of immunity: 1) Non-specific immunity 2) Specific immunity

3. 1) Non-specific Immunity
This is our ability to prevent any bad agent (pathogen) from infecting our body.
examples: a) skin b) mucus membranes c) inflammation d) interferons

4. a) Skin Covers the body so a pathogen can’t get in.
Skin is also slightly acidic so bacteria cannot live on it.
Upper layer of skin (called the epidermis) is dead and waterproof.
Epidermis has the protein Keratin to make it strong (so it doesn’t break open)
The dermis (lower skin layer) contains oils & sweat glands. Oil on our skin contains antibodies to kill pathogens.

5. b) Mucus membranes
Nasal passages are lined with hair & mucus to trap pathogens before they get into the lungs
Mucus also lines parts of the digestive system and reproductive system in order to prevent pathogens from entering.

6. c) Inflammation
When you get a cut or insect bite, your white blood cells move to the site of injury.
These white blood cells prevent the pathogen from getting farther into the body.
The heat from the inflammation helps to kill some pathogens and prevents them from spreading.

7. d) Interferons
These are proteins that are secreted by cells once they are infected by a virus.
Interferons alert other cells that a virus is in the body.
3 types of interferons: 1) fights viruses 2) fights bacteria 3) another fights various pathogens

8. 2) Specific Defenses
These include cells in our body that fight specific pathogens in the body. (They work together to kill almost any invader)
There are two types of specific immunity: a) Humoral immunity (B-cells) b) Cell-mediated immunity (T-cells)
Video

9. a) Humoral immunity
B-cells (or B Lymphocytes) make antibodies to ciruculate in the blood and lymph (lymph glands).
When a pathogen enters the body, our B-cells recognize what kind of pathogen it is.
For EVERY pathogen there is ONE type of antibody that fights it.
Video

10. a) Humoral immunity cont…
B-cells DO NOT destroy cells. They do 2 things: 1) make the toxin released from the pathogen less dangerous (so we don’t get as sick) 2) clump many pathogen cells together so they are easier to destroy

11. b) Cell-mediated immunity
T-cells destroy pathogens in our body. (2 types of T-cells)
1) Cytotoxic T-cells
Kill cells that have released interferon (or cells that are infected)
2) Helper T-cells
Help identify infected cells so cytotoxic t-cells know what to “target”

12. What is immunity?
Resistance to a disease causing organism or harmful substance
Two types
Active Immunity
Passive Immunity

13. Active Immunity You produce the antibodies
Your body has been exposed to the antigen in the past either through:
Exposure to the actual disease causing antigen – You fought it, you won, you remember it
Planned exposure to a form of the antigen that has been killed or weakened – You detected it, eliminated it, and remember it
What is this second type of exposure called?

14. Vaccine
Antigens are deliberately introduced into the immune system to produce immunity
Because the bacteria has been killed or weakened, minimal symptoms occur
Have eradicated or severely limited several diseases from the face of the Earth, such as polio and smallpox

15. How long does active immunity last?
It depends on the antigen
Some disease-causing bacteria multiply into new forms that our body doesn’t recognize, requiring annual vaccinations, like the flu shot
Booster shot - reminds the immune system of the antigen
Others last for a lifetime, such as chicken pox

16. Think the flu is no big deal?
Think again…
In 1918, a particularly deadly strain of flu, called the Spanish Influenza, spread across the globe
It infected 20% of the human population and killed 5%, which came out to be about 100 million people

17. Do we get all the possible vaccines we can?
Although the Center for Disease Control (CDC) recommends certain vaccines, many individuals go without them
Those especially susceptible include travelers and students
Consider the vaccine for meningitis, which is recommended for all college students and infects 3,000 people in the U.S., killing 300 annually
Link

18. Passive Immunity You don’t produce the antibodies
A mother will pass immunities on to her baby during pregnancy
These antibodies will protect the baby for a short period of time following birth while its immune system develops.
Lasts until antibodies die
Thymus
Placenta

19. Immune Disorders ~Allergies~
Immune system mistakenly recognizes harmless foreign particles as serious threats
Launches immune response, which causes sneezing, runny nose, and watery eyes
Anti-histamines block effect of histamines and bring relief to allergy sufferers

20. Aquired Immune Deficiency Syndrome
Caused by the Human Immunodeficiency Virus
Discovered in 1983
Specifically targets and kills T- cells
Because normal body cells are unaffected, immune response is not launched

21. AIDS ~The Modern Plague~
The HIV virus doesn’t kill you – it cripples your immune system
With your immune system shut down, common diseases that your immune system normally could defeat become life- threatening
Can show no effects for several months all the way up to 10 years

22. AIDS ~The Silent Spread~
Transmitted by sexual contact, blood transfusions, contaminated needles
As of 2007, it affects an estimated million people