The Immune System

1. The Immune System Chapter 35

2. For thousands of years, people thought diseases were caused by curses, evil spirits, or vapors rising from foul marshes or dead plants and animals.

3. This isn’t at all surprising, because until microscopes were invented, most causes of disease were invisible to the human eye!

4. AGENTS OF DISEASE Infectious diseases are caused by pathogens- organisms that invade the body and disrupt its normal functioning Examples: viruses, bacteria, single-celled eukaryotes, fungi, and parasites

5. VIRUSES • Cause the common cold, influenza (the flu), and warts • Nonliving particles that replicate by inserting their genetic material into a host cell and taking over many of the host cell’s functions

6. BACTERIA • Cause strep infections, diphtheria, botulism, and anthrax • Cause disease by breaking down the tissues of an infected organism for food, or by releasing toxins that interfere with normal activity in the host.

7. FUNGUS • Trichophytoninterdigitalecauses athlete’s foot • May infect the surface of the skin, mouth, throat, fingernails, and toenails. Dangerous infections may spread from the lungs to other organs.

8. Single-Celled Eukaryotes • Plasmodium is carried by insects and causes malaria • Trypanosomabruceicauses African Sleeping Sickness by feeding off nutrients in the host’s blood • Giardiaintestinalisinfects the digestive tract and is transmitted in infected water

9. Plasmodium

10. PARASITES (YIKES!) • Trichinellaspiralis comes from eating infected pork (a roundworm) • Schistosomamansonican infect people working in rice paddies (a flatworm) • Tapeworms and hookworms can also infect people WARNING…PICTURES OF THESE ON THE NEXT SLIDE!

11. TAPEWORM ROUNDWORM HOOKWORM FLATWORM

12. Symbionts vs. Pathogens Symbionts are the “good” bacteria and organisms that live in the body without causing disease. These are helpful organisms that aid in digestion and produce vitamins. Pathogens cause problems, but symbionts do not interfere with the normal functioning of the body.

13. ZOONOSES- animals as vectors Zoonotic Diseases are transferred from animal host to a human host. West Nile virus is carried by mosquitos and can transfer the virus between birds and humans Being bitten by an infected animal, coming in contact with its wastes, or eating the meat can transfer infections as well. End of 35.1

14. How do infectious diseases spread? • Bodily fluids • Contaminated water or food • infected animals • Coughing • Sneezing • physical contact Click here if you are ready to do the activity

15. If pathogens are all around us, why are we usually disease free? Why do we usually recover from the pathogens that do infect us?

16. One reason is that our bodies have an incredibly powerful and adaptable series of defenses that protect us against a wide range of pathogens

17. A QUICK CLIP This video clip is a “fun” introduction to how your immune system works Click on the popcorn…I don’t really have popcorn for you to eat while you watch, so I guess it was rather mean to bring it up at all. Make sure the speakers are on!

18. FIRST LINE OF DEFENSE • Nonspecific defenses are the same no matter what type of pathogen is present (physical & chemical barriers) • Skin, tears, saliva, mucus, stomach juices

19. SECOND LINE OF DEFENSE If pathogens make it through the first line… • INFLAMMATORY RESPONSE • INTERFERON • FEVER These are still nonspecific defenses!

20. INFLAMMATORY RESPONSE • Infected areas become red, painful, or inflamed because the mast cells are stimulated to release histamines. More blood flowing to the area will bring more white blood cells & may raise the temperature of the area

21. INTERFERONS • Proteins that “interfere” with viral growth • Slow down the progress of infection and buys time for specific immune defenses to respond

23. FEVER Certain chemicals released by the immune system increase body temperature • May slow down or stop the growth of pathogens • Speeds up several parts of the immune response

24. SPECIFIC DEFENSES • Recognizing “Self”: antigens on cells that belong in the body prevent attacks by a healthy immune system. • Recognizing “Nonself”: immune system recognizes, responds to, and remembers foreign organisms (they have different antigens). This is called immune response.

25. SPECIFIC DEFENSES continued Antibodies, made by white blood cells, “tag” foreign antigens for destruction by immune cells Only one antibody fits with one antigen. That’s why a flu shot does not prevent the chicken pox!

26. ORGAN TRANSPLANTS • Antigens on the new organ’s cells are targeted for destruction by the immune system. This is known as rejection. • Donors & recipients need to have nearly identical cell markers • Drugs to suppress the immune system must be taken for the rest of the recipient’s life to prevent rejection (immunosuppressant medications). End of 35.2

27. ACTIVE IMMUNITY • May develop as a result of natural exposure to an antigen (fighting an infection) or from deliberate exposure (through a vaccine). This kid got the vaccine This kid didn’t But they both have active immunity.

28. WHAT IS A VACCINE? • Contains a dead or weakened form of a pathogen • Stimulates the immune system by introducing a specific antigen • The immune system recognizes and remembers the foreign antigen which will speed up the response when the antigen appears again.

29. PASSIVE IMMUNITY • Temporary immunity- the body will eventually destroy the foreign antibodies • Can be due to natural exposure (mother to fetus) or deliberate exposure (injection of antibodies from another source)

30. PUBLIC HEALTH MEASURES • Help prevent disease by regulating food and water supplies, promoting vaccination, and promoting ways to prevent infection • Antibiotics (medications) can kill bacteria and some antiviral medications can slow down viral activity

31. NEW AND RE-EMERGING DISEASES • Humans and animals merging habitats & exotic animal trade increases risk of new infections • Misuse of medications has led to the re-emergence of old diseases we thought were under control

32. MISUSE OF MEDICATIONS • Some pathogens are evolving into antibiotic resistant forms (the usual antibiotics do not kill them). This is due to overuse of medications. • Measles is making a comeback because some people do not follow the vaccination recommendations. End of 35.3

33. IMMUNE SYSTEMS DISORDERS • Sometimes, the immune system attacks the wrong targets • Other times, the immune system itself is disabled by the disease What happens in these cases?

34. EXAMPLES • Allergies- overreaction of immune system to normally harmless antigens • Asthma-allergic reactions in the respiratory system that causes narrowing of the air passageways • Autoimmune Diseases- Immune system attacks the body’s own cells. Type I Diabetes, Lupus, Rheumatoid Arthritis

35. HIV & AIDS • Human Immunodeficiency Virus- causes AIDS • Acquired ImmunoDeficiencySyndrome = AIDS Just looking at the names, what does it do?

36. Why is it bad? • HIV can hide from the immune system • It attacks key cells within the immune system, leaving the body unprepared to fight other pathogens

37. HOW IS HIV TRANSMITTED? • Infected blood, sexual contact, or breast milk CAN IT BE CURED? • No cure yet, but new drugs make it possible to survive HIV infection for years. • The virus is rapidly evolving and some strains are resistant to current medications

38. ACTIVITY: How are infectious diseases spread? • Take a cup of “bodily fluids”. • Round 1- Pour the entire contents of your cup into your partner’s cup. Your partner will pour ½ back into your cup. • Round 2- Repeat the process for Round 1, but mix fluids with a DIFFERENT person. • Get tested to see if you are infected!

39. ACTIVITY CONCLUSION • Why were only some of you infected? • How could the infected individuals have avoided being infected? • This activity demonstrates how an infection like chicken pox or pink eye can spread. Why do you think real infections take longer to “show up” than our pretend infection? DONE

40. …FOR TODAY