1. Unit 8- THE IMMUNE SYSTEM

2. Immunity
Immunity
The ability of the body to fight infection and/or foreign invaders by producing antibodies or killing infected cells.
Immune System
The system in the body responsible for maintaining homeostasis by recognizing harmful from nonharmful organisms.

3. Foreign Invaders Called Pathogens
Viruses, bacteria or parasite that causes disease/immune response.
Toxins that pathogens produce may cause harm as well.

4. Parts of the Immune System
Blood - White Blood Cells in particular
Lymph nodes
Thymus Gland – Produces T Cells
Bone Marrow – Produces B Cells

5. The Body’s THREE lines of Defense
First Line of Defense – The Skin
Provides Physical and Chemical barriers
Physical – hard to penetrate, made of indigestible keratin
Chemical – tears, sweat

6. Second Line of Defense – Nonspecific Immune Response
These are defenses the body uses no matter what the invader may be. These defenses include:
Phagocytosis – done by macrophages
Natural Killer Cells
Inflammation - caused by release of histamine.
Fever – caused by histamines. The fever (high temp) kills invaders.

7. Third Line of Defense
This is a specific response to a specific pathogen.
The response involves the creation of antibodies and killer cells.

8. White Blood Cells
B-cells mature in bone marrow then concentrate in lymph nodes and spleen-Produce antibodies
T-cells mature in thymus
B and T cells mature then circulate in the blood and lymph
Circulation ensures they come into contact with pathogens

9. B Cells
Activated B cells produce lots of antibodies, about a 1000/sec.
The antibodies travel to the blood, lymph, lining of gut and lungs.
Antibodies stay in the blood longer but eventually their numbers go down.

10. B -Lymphocytes Some activated B cells become memory cells.
Memory cells divide rapidly as soon as the pathogen is reintroduced.
When the pathogen/infection infects again it is destroyed before any symptoms show.

11. T-Cells Two types: Helper T cells -help the immune response start
Killer T cells
-Kill body cells making new pathogen
Memory T cells
-remain in body

12. The Immune Response Explained
Pathogens infect cells.
Macrophage ingests pathogen and displays portion on its surface.
Helper T- Cell recognizes pathogen on the surface of the macrophage and becomes active.
Helper T-Cell activates Killer T-Cells and B-Cells.

13. The Immune Response Explained
5. Killer T-Cells kill infected cells.
6. At the same time, B-Cells start making antibodies which kill already made pathogens.
7. Memory T and Memory B cells remain in the body to speed up the response if the same antigen reappears.

14. Active and Passive Immunity
Active immunity
Lymphocytes are activated by antigens on the surface of pathogens
Natural active immunity - acquired due to infection
Artificial active immunity – vaccination
Takes time for enough B and T cells to be produced to mount an effective response.

15. Active and Passive Immunity
Natural passive immunity
A mother’s antibodies pass across the placenta to the fetus and remain for several months.
Colostrum (the first breast milk) contains lots of antibodies which help the baby fight infection

16. Vaccines A preparation containing anti-pathogen material:
Whole live microorganism
Dead microorganism

17. Vaccines Why aren’t they always effective?
Natural infections persist within the body for a long time so the immune system has time to develop an effective response, vaccinations from dead pathogens do not do this.
Less effective vaccines need booster injections to stimulate secondary responses

18. Allergies When the immune system responds to harmless substances
Allergens – substances which do no real harm
Allergens include house dust, animal skin, pollen, house dust mites and their feces

19. Autoimmune Diseases A. Autoimmune Diseases
- Occur when the immune system no longer recognizes the cells of your own body… the immune system attacks healthy body cells.
Examples include:
Diabetes Mellitus
Lupus
Multiple Sclerosis (MS)
Rheumatoid Arthritis
Autoimmune diseases are more frequent in women than in men due to hormonal differences
These diseases are treated with drugs that suppress the immune system as well as with antibodies that attack lymphocytes

20. Autoimmune Diseases
Diabetes Mellitus (Type I or Juvenile Onset) -The immune system destroys the Insulin producing cells of the pancreas. Multiple Sclerosis -occurs when the body attacks its own neurons. -effects include the loss of motor control, feeling or even paralysis of the affected areas. -MS generally attacks the neurons of the optic nerves, the brain and the spinal cord.

21. Autoimmune Diseases Rheumatoid Arthritis
The body’s own antibodies attack and destroy tissue at the joints
The condition is chronic, with episodes of pain and swelling
No cure, but patients may have joints removed and replaced by artificial ones

22. Immune System Diseases
B. Immune Deficiencies
- The inability of the immune system to protect the body from pathogens.
Severe Combined Immune Deficiency (SCID)
HIV/AIDS

23. Immune System Diseases
HIV/AIDS (Human Immunodeficiency Virus)
Attacks and kills Helper T Cells. Without these cells, circulating antibodies drop in number and the body is left more vulnerable to other invading pathogens.

24. Organ Transplants Organ Transplants and Rejection
If the body receives tissue from another person or animal the body will recognize this tissue as foreign
An immune response will be started against the new tissue
If the immune system isn’t repressed, the new tissue will be rejected
This is why organ donors are closely matched to their recipients