1. The Immune System Lymphatic system Immune system disorders
Defence system
Immune system disorders

2. The Immune System
Inside your body there is an amazing protection mechanism called the immune system. It is designed to defend you against millions of bacteria, microbes, viruses, toxins and parasites (pathogens) that would love to invade your body

3. THE LYMPHATIC SYSTEM
A network of vessels and nodes throughout the body
Lymph is a pale, yellow interstitial fluid (similar to blood plasma)

4. Lymph serves to maintain fluid balance in the body
Lymph nodes contain lymphocytes and macrophages (phagocytic monocytes) which serve to trap & destroy bacteria

5. LYMPH NODES

6. Fighting Bacteria & Viruses
Viral and bacterial infections are by far the most common causes of illness for most people. They cause things like colds, influenza, measles, mumps, malaria, AIDS and so on. The job of your immune system is to protect your body from these infections. The immune system protects you in three different ways:

7. Fighting Bacteria & Viruses
It creates a barrier that prevents bacteria and viruses from entering your body. (eg – skin)
If a bacteria or virus does get into the body, the immune system tries to detect and eliminate it before it can make itself at home and reproduce. (eg – phagocytic white blood cells)
If the virus or bacteria is able to reproduce and start causing problems, your immune system is in charge of eliminating it. (eg – B and T cells)

8. The Immune System is the Third Line of Defense Against Infection

9. Nonspecific Defenses (FIRST LINE - Physical Barriers)
Figure 22.10

10. Nonspecific Defenses (SECOND LINE - Phagocytes)
Figure 22.10

11. Nonspecific Defenses (SECOND LINE - Immunological Surveillance) Natural killer T cells (cytotoxic T cells) destroy body cells that have become cancerous or infected by viruses
Figure 22.10

12. Nonspecific Defenses (SECOND LINE – Complement System)
Figure 22.10

13. Specific Defences (Antibody-Mediated Immunity)
Antibodies are proteins that recognize foreign substances (antigens) and try to neutralize or destroy them.
Antibodies are produced by LYMPHOCYTES

14. White Blood Cells
All white blood cells are known officially as Leukocytes.
White blood cells are not like normal cells in the body - they actually act like independent, living single-cell organisms able to move and capture things on their own.

15. White Blood Cells
White blood cells behave very much like amoeba in their movements and are able to engulf other cells and bacteria.

16. White Blood Cells
Many white blood cells cannot divide and reproduce on their own, but instead have a factory somewhere in the body that produces them. That factory is the bone marrow.

17. Antibodies and Complement Proteins
Antibodies are produced by white blood cells.
They are Y-shaped proteins that each respond to a specific antigen (bacteria, virus or toxin).
Each antibody has a special section (at the tips of the two branches of the Y) that is sensitive to a specific antigen and binds to it in some way.

18. Antibodies and Complement Proteins
When an antibody binds to the outer coat of a virus particle or the cell wall of a bacterium it can stop their movement through cell walls. Or a large number of antibodies can bind to an invader and signal to the complement system that the invader needs to be removed.

19. The immune system response
Antigen triggers an immune response
Activates T cells and B cells
T cells are activated after phagocytes exposed to antigen
T cells attack the antigen and stimulate B cells
Activated B cells mature and produce antibody
Antibody attacks antigen

20. An Overview of the Immune Response
Figure 22.15

21. Major types of T cells
Cytotoxic (Killer) T cells – attack foreign cells – pucture a hole in cell membrane
Helper T cells – activate other T cells and B cells
Suppressor T cells – inhibit the activation of T and B cells – make sure normal tissue isn’t destroyed
Memory T cells – remain in bloodstream and can act quickly if antigen comes into blood again

22. Types of Immunity
Figure 22.14

23. IMMUNE SYSTEM DISORDERS
ALLERGIES
An allergy is an exaggerated response of the immune system to a harmless material (eg – pollen, pet dander, grass, peanuts, etc)

24. ALLERGIES 2 types of allergic reactions: Immediate (or acute) Delayed
- occurs within seconds of exposure – disappears within 30 minutes
(eg) pets, nuts, pollen
Delayed
- reaction is slower and lasts longer
- T-cells are sensitized by previous contact
(eg) cosmetics, jewellery

25. What happens during an immediate allergic reaction?
Specialized antibodies trigger certain cells to release histamines
Histamines are chemicals that increase the permeability of blood vessels
Therefore, blood (mostly plasma with some WBCs) leaks out of the vessels and into the tissues – causing them to become red and swollen
Symptoms: itchy, puffy eyes, runny nose, constriction of airways (asthma, or anaphylaxis)

26. What is anaphylaxis?
Anaphylaxis is a severe allergic reaction to a specific allergen – eg peanuts, bee stings, etc.
Airways can close almost immediately – which can be fatal
An injection of adrenaline (Epi-pen) is given

27. COMMON ALLERGENS

28. AUTOIMMUNE DISORDERS
Your body identifies your own cells as “self” cells
Sometimes, T cells or antibodies make mistakes and attack your own cells, mistaking them for “non-self” cells
An autoimmune disorder is the result
EXAMPLES: rheumatoid arthritis, Type I diabetes

29. RHEUMATOID ARTHRITIS A chronic autoimmune disorder
Characterized by inflammation of the joints
Most common in people years
Immune system attacks bone, cartilage, ligaments