1. The Immune System

2. Why an Immune System?
Defends the body against pathogens (disease-causing organisms), toxins, and cancer cells.
Includes both non-specific and specific responses.

3. The Immune System

4. Non-specific Immunity
Skin
Ciliated/mucus membranes of respiratory tract trap and sweep away foreign particles
Tears and saliva contain enzymes that break down bacterial cell walls
Non-pathogenic bacteria of skin, mouth, intestines, vagina, etc. out-compete pathogens
Macrophages consume all foreign material it encounters
A macrophage engulfs rod-shaped bacteria

5. Specific Immunity
Targets specific pathogens (bacteria, viruses, cancer cells, or infected body cells).
Works by detecting antigens – foreign proteins on the surface of pathogens that induce a specific immune response.
Includes cell-mediated and antibody-mediated responses.

6. Antigen Presentation

7. Cell-mediated Response
Macrophages that have ingested pathogens present antigens on cell surface to helper T-cells.
Helper T-cells can produce chemicals called lymphokines that may activate killer T-cells.
Killer T-cells can bind to and kill infected cells.

8. Cell-mediated Response

9. Antibody-mediated Response
Lymphokines from helper T-cells activate B-cells to become plasma B-cells.
Plasma B-cells produce free antibodies into blood, bind to specific antigens causing them to clump together. This clumps pathogens making it easier for macrophages to consume them.
Other B-cells become memory B-cells which can reactivate the immune system quickly upon reinfection.

10. Antibodies Bind to Antigens

11. Antibody-mediated Response

12. Inflammatory Response – an important nonspecific defense
*phagocytes = macrophages

13. Allergies
Allergies result from immune cells that over-respond to non-pathogenic substances.
Allergens (pollen, dust, egg whites, etc.) stimulate mast cells to produce chemicals called histamines.
Histamines produce symptoms associated with inflammation (itching, swelling, redness, etc.)

14. Late-stage rheumatoid arthritis; an autoimmune disorder
Autoimmune Diseases
When the immune system mistakes body cells for pathogens, the result is an autoimmune disease.
Autoimmune disorders result in destruction of healthy tissues by killer T cells.
Examples: Type 1 Diabetes, Rheumatoid Arthritis, Multiple Sclerosis, Lupus
Late-stage rheumatoid arthritis; an autoimmune disorder

15. Immune Disorders are on the Rise

16. Vaccines
Vaccines are solutions of killed, weakened, or disassembled pathogens.
Vaccines stimulate production of antibodies and memory cells without infection or disease.