THE IMMUNE SYSTEM

1. 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 non-harmful organisms and produces an appropriate response.

3. Foreign Invaders • Called Pathogens • Viruses, bacteria or other living thing that causes disease or an immune response. • Antigens • Toxins that pathogens produce that cause harm to an organism. (Anything identified as non-self)

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

5. The Body’s 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. Nonspecific Immune Response Second Line of Defense - These are defenses the body uses no matter what the invader may be. These defenses include: • Phagocytosis –done by macrophages • Natural Cell Killers • Inflammation - caused by release of Histamine from leukocytes • Fever – caused by histamines. The fever (high temp) kills invaders by denaturing their proteins.

8. Specific Immune Response Third Line of Defense – This is a specific response to a specific pathogen/antigen. • The response involves the creation of antibodies.

9. Cells of the Immune System White Blood Cells • Phagocytes - Neutrophils - Macrophages • Lymphocytes

10. Neutrophils • 60% of WBCs • ‘Patrol tissues’ as they squeeze out of the capillaries. • Large numbers are released during infections • Short lived – die after digesting bacteria • Dead neutrophils make up a large proportion of puss.

11. Macrophages • Larger than neutrophils. • Found in the organs, not the blood. • Made in bone marrow as monocytes, called macrophages once they reach organs. • Long lived • Initiate immune responses as they display antigens from the pathogens to the lymphocytes.

12. The Immune Response Explained • Antigen infects cells. • Macrophageingests antigen and displays portion on its surface. • Helper T- Cell recognizes antigens on the surface of the macrophage and becomes active. • Active Helper T-Cell activates Cytotoxic T-Cells and B-Cells. • Cytotoxic T-Cells divide into Active Cytotoxic T-cells and Memory T – Cells.

13. The Immune Response Explained 6. Active Cytotoxic T-Cells kill infected cells. 7. At the same time, B-Cells divide into Plasma Cells and Memory B- Cells. 8. Plasma cells produce antibodies that deactivate pathogens. 9. Memory T and Memory B cells remain in the body to speed up the response if the same antigen reappears. 10.Supressor T-Cells stop the immune response when all antigens have been destroyed.

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 Passive immunity • B and T cells are not activated and plasma cells have not produced antibodies. • The antigen doesn’t have to be encountered for the body to make the antibodies. • Antibodies appear immediately in blood but protection is only temporary.

16. Active and Passive Immunity Artificial passive immunity • Used when a very rapid immune response is needed e.g. after infection with tetanus. • Human antibodies are injected. In the case of tetanus these are antitoxin antibodies. • Antibodies come from blood donors who have recently had the tetanus vaccination.

17. 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 IgA which remain on surface of the baby’s gut wall and passes into blood.

18. Autoimmune Diseases • Autoimmune diseases are diseases where the immune system begins to attack itself. • Ex: • Rheumatoid Arthritis – crippling disease of the joints. • Lupus – disease of blood and organs. • Multiple Sclerosis – disease of nervous system • Cause(s): unknown • Cures/Treatments: No known cures. Usually treated with drugs.