1. The Human Immune System
Video

2. The Immune System Overview
Innate (nonspecific) defense mechanisms
Adaptive (specific) defense mechanisms
First Line of Defense
Second Line of Defense
Third Line of Defense
Skin
Mucous Membranes
Secretions of skin and mucous membranes
Phagocytic Cells
Antimicrobial proteins
The inflammatory response
Lymphocytes
Antibodies
Macrophages

3. What is the immune system?
The body’s defense against disease causing organisms, malfunctioning cells, and foreign particles

4. The First Line of Defense ~Skin~
The dead, outer layer of skin, made up of keratinized epidermis, forms a physical shield against invaders and secretes chemicals that kill potential invaders
You shed between 40 – 50 thousand skin cells every day!

5. The First Line of Defense ~Acidic pH of skin secretions~
Skin’s acidic secretions inhibit bacterial growth
Sebum contains chemicals that are toxic to bacteria
Vaginal secretions in females are very acidic.

6. The First Line of Defense ~Mucus and Cilia~
As you breathe in, foreign particles and bacteria bump into mucus throughout your respiratory system and become stuck
Hair-like structures called cilia sweep this mucus into the throat for coughing or swallowing
Don’t swallowed bacteria have a good chance of infecting you?

7. The First Line of Defense ~Saliva~
What’s the first thing you do when you cut your finger?
Saliva contains lysozyme, an enzyme that breaks down bacteria
Thousands of different types of bacteria can survive saliva

8. The First Line of Defense ~Stomach Acid~
Swallowed bacteria are broken down by incredibly strong acids in the stomach that break down your food
The stomach must produce a coating of special mucus or this acid would eat through the stomach!

9. Think of the human body as a hollow plastic tube…
The food is digested within the hole in the tube, but it never actually enters into the solid plastic material.
Tube inner surface ~Digestive System~
Tube outer surface ~Skin~
Plastic interior ~Body~

10. Escherichia coli is common and plentiful in all of our digestive tracts. Why are we all not sick?
These bacteria are technically outside the body and aid in digesting material we cannot
Only if E.Coli are introduced in an unnatural manner can they break through the first line of defense and harm us

11. Second Line of Defense
Non-Specific response – do not target specific cells
Include:
Phagocytes
Macophages
Complement Proteins
Inflammation

12. The Second Line of Defense ~White Blood Cells~
If invaders actually get within the body, then your white blood cells (WBCs) begin their attack
WBCs normally circulate throughout the blood, but will enter the body’s tissues if invaders are detected
Video

13. Where could invaders hide from phagocytes?
White Blood Cells
~Phagocytes~
These white blood cells are responsible for eating foreign particles by engulfing them
Once engulfed, the phagocyte breaks the foreign particles apart in organelles called ________
Lysosomes
Where could invaders hide from phagocytes?

14. Phagocytosis by a macrophage

15. Second Line of Defense ~ Antimicrobial Proteins~
Enhance defenses by attacking microorganisms directly or by hindering their ability to reproduce.
Most Common:
Complement Proteins
Interferons

16. Complement Proteins
Consists of ~20 plasma proteins that circulate the blood in an inactive state.
They become activated by attaching to pathogens such as bacteria and fungi.
Once activated they form a membrane attack complex (MAC).
Punches holes in pathogens allowing water to leak in and causes them to burst!
Enhances phagocytosis and intensifies inflammatory response.

18. Cell before infection…
Viruses
Viruses enter body cells, hijack their organelles, and turn the cell into a virus making-factory. The cell will eventually burst, releasing thousands of viruses to infect new cells.
…and after.
Cell before infection…

19. The Second Line of Defense ~Interferons~
Virus-infected body cells release interferon when an invasion occurs
Interferon – chemical that interferes with the ability for viruses to attack other body cells
What happens to already infected cells?

20. White Blood Cells ~Natural Killer Cells~
Natural killer cells, police the body in blood and lymph and recognize infected human cells and cancer cells
They are not picky about which non-self cells to attack.
NK cells attack target cells membrane and release a lytic chemical called perforin, killing the cell.

21. The Second Line of Defense ~The Inflammatory Response~
Injured body cells release chemicals called histamines, which begin inflammatory response
Capillaries dilate
Temperature rises
Pain receptors activate
WBCs flock to infected area like sharks to blood called “chemotaxis”

23. Homeostatic Imbalance
PUS = mixture of dead or dying neutrophils, broken down tissue cells, and living and dead pathogens.
ABSCESSES = failure of inflammatory response to clear area of debris, pus becomes walled off and often needs to be surgically drained before healing occurs.

24. PUS & ABSCESS

25. The Third Line of Defense ~Antibodies~
Most infections never make it past the first and second levels of defense
Those that do trigger the production and release of antibodies
Proteins that latch onto, damage, clump, and slow foreign particles
Each antibody binds only to one specific binding site, known as an antigen

26. Antibody Production
WBCs gobble up invading particles and break them up
They show the particle pieces to T-cells, who identify the pieces and find specific B-cells to help
B-cells produce antibodies that are equipped to find that specific piece on a new particle and attach
Video - 1:58

27. Defenses Against Disease (cont.)
Two major types of lymphocytes
B Cells and T Cells
Response
Recognize antigens in the body
B cells
Respond to antigens by becoming plasma cells
Plasma cells make antibodies
Memory B cells produce stronger response with next exposure to antigen
T Cells
Cell-mediated response
Bind to antigens on cells and attack them directly
Secrete lymphokines that increase T cell production and directly kill cells with antigens

28. Immunity
New particles take longer to identify, and a person remains ill until a new antibody can be crafted
Old particles are quickly recognized, and a person may never become ill from that invader again. This person is now immune.

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

31. 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?

32. 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

33. 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

34. 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

35. 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

36. Passive Immunity You don’t produce the antibodies
A mother will pass immunities on to her baby during pregnancy - through what organ?
These antibodies will protect the baby for a short period of time following birth while its immune system develops. What endocrine gland is responsible for this?
Lasts until antibodies die
Thymus
Placenta
Why doesn’t the mother just pass on the WBCs that “remember” the antigens?

37. 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

38. Acute hypersensitivity
Triggered by release of a flood of histamine when antibodies bind to mast cells.
Histamine dilates small blood vessels causing: a runny nose, watery eyes, and itching.
Anaphylactic shock: when allergen enters the blood.

39. Delayed hypersensitivity
Cytokines are released instead of histamine
Cortisone drugs are used for relief
Most familiar examples are classed as allergic contact dermatitis.
Poison ivy, deodorant chemicals, cosmetics

40. 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

41. 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

42. AIDS ~The Silent Spread~
Transmitted by sexual contact, blood transfusions, contaminated needles
As of 2007, it affects an estimated 33.2 million people

43. Bubonic Plague
Caused by a bacterium called Yersinia pestis, is transmitted from rodent to rodent by fleas

44. Botulism
A rare but serious paralytic illness caused by a nerve toxin that is produced by a bacteria. There are three main kinds: foodborne, wound, and infant. Toxin has also been used cosmetically.

45. Botulism

46. Tuberculosis
A disease caused by bacteria that are spread from person to person through the air. this disease usually affects the lungs, but it can also affect other parts of the body, such as the brain, the kidneys, or the spine; active and latent forms exist; common diagnosis is from a skin test.

47. TB