1. The Human Defence System

2. What I need to know from this chapter
General defence system
skin, mucous membrane of the breathing system, reproductive and digestive tracts. Phagocytic white blood cells
Specific defence system
Antigen antibody response
Definition of “induced immunity”
Vaccination & immunisation
Role of lymphocytes B & T cell types
Role of B cells in antibody production, Role of t cells as helpers, killers, suppressors and memory t cells.

3. General Defence System
Non specific
Acts against all pathogens
Consists of two parts

4. 1st Part of Defence System
Skin
Mucus
clotting
Lysozyme
Cilia
Acid
Sebaceous gland
Good bacteria
2nd Part of the Defence System
Phagocytic white blood cells
Inflammation
Defence Proteins/complement system

5. Skin (1st Line defence)
Skin – provides a structural barrier to infection
Clotting – prevents entry of pathogens
Lysozyme – Enzyme found in sweat, tears, saliva
- Dissolves cell walls of bacteria
Sebaceous glands – chemicals to kill bacteria

6. Respiratory Tract (1st Line defence)
Respiratory tract lined with mucus
-Traps pathogens
Respiratory tract has cilia
- Moves mucus back up into the throat
- carries pathogens out

7. Digestive Tract (1st Line defence)
Produces mucus
Produces acid in the stomach
- kills many bacteria

8. Reproductive tract (1st Line defence)
Beneficial bacteria in vagina produce lactic acid – prevents growth of pathogens

10. Phagocytic White Blood Cells (2nd Line Defence)
Micro organisms that damage cells
These cells release chemicals
The chemicals attract white blood cells
White blood cells engulf pathogens
White blood cells that engulf pathogens are called Phagocytes
Large phagocytes called Macrophages – found in Spleen, Tonsils, Adenoids
Filter out pathogens from lymph system

11. Phacocytosis -White Blood Cells
“Eating” germ
Germ
White cell

12. Inflammation (2nd Line Defence)
Infected cells release histamine
This causes dilation (widening) of blood vessels
The wider the vessel the easier white blood cells can get to the area
Which causes vessels to become porous
General Inflammation causes a fever
High temperature stops bacteria reproducing

13. Defence Protein (2nd Line Defence)
Complement system-group of 20 proteins found in blood plasma
When activated they destroy viruses and other pathgen’s by creating a hole in the pathogens cell membrane which make them burst.

14. Specific Defence System (The Immune System)
Attacks particular pathogens
Produces antibodies which kill pathogens
Produces white blood cells

15. White Blood Cells Leucocytes
Lymphocytes attack cells that contain antigens
Lymphocytes produce antibodies
Monocytes develop into macrophages
Macrophages recognise antigens (foreign molecules)
Digest the pathogens & antigens are displayed on the outside of the macrophage this stimulates the production of antibodies

16. Antibodies
An antigen are chemicals that are on the surface of a pathogen
An antibody produced by lymphocytes in response to an antigen

17. Antibodies

18. What antibodies do
Prevent viruses and bacteria from entering new host cells
Label pathogens to be destroyed by phagocytes
Antibodies can inactivate pathogens by making them clump together
Can trigger the complement system –
This causes pathogen cells to burst

19. Complement Protein
Pathogen Clump

20. Antigen Antibody Reaction
Highly specific
Each antigen stimulates the production of one antibody
Why we get flu every year
Different strain

21. Problems Can be disabled - AIDs
Body produces antibodies against its own tissues
Rheumatoid Arthritis
Multiple Sclerosis
Allergies

22. Duration of Immunity After infection antibodies remain
1st time an antigen is produced
14 days to produce maximum no. of antibodies
Subsequent infection – 5 days

23. Induced Immunity
Is the ability to resist disease caused by specific pathogens by the production of antibodies.
2 Types of immunity
1. Active Passive

24. Active Immunity
Production of your own antibodies in response to antigens.
Is longer-lasting
Can be induced naturally or artificially
Natural Active Immunity
Occurs when pathogen enters body in normal way.
Artificial Active Immunity
Vaccine is a non disease-causing dose of pathogen, which triggers the production of antibodies
Pathogens in vaccine’s are killed/treated (No reproducing)
Modern vaccines are genetically engineered

25. Passive Immunity Given antibodies that were formed by other organisms
Short term resistance (Few weeks to 6 months)
Induced in 2 ways:
Natural Passive Immunity
Child gets antibodies from mother
Either through the placenta or mothers milk
Artificial Passive Immunity
Given an injection with antibodies produced by other organism. i.e. Anti-tetanus injection (from horses)

26. Advanced Study of Lymphocytes
2 Types (mature in different places)
B-lymphocytes (B-cells)
–Bone Marrow
T-lymphocytes (T-cells)
– Thymus Gland

27. B-Cells When matured move from bone marrow to lymphatic tissue
–Esp. Spleen and Lymph nodes
There are millions
Each adapted to recognise 1 specific antigen
Produces only 1 type of antibody

28. B-Cells
Divides & produces more B-cells (Plasma cells) on contact with antigen
Plasma cells -short lived, produce 2000 AB a second
Anti-bodies AB inactivate antigen by attaching to them
Disposed 1. phagocytes
2. Complement system (cells burst)

29. B-Cells Some B-cells remain alive = memory B-cells
Secondary response is more effective
Produces antibodies to small amounts of antigen
Much faster response
Greater numbers of antibodies
Active in controlling bacterial infections

30. T-Cells Activated when they move from bone marrow to Thymus
Thymus is most active in weeks before & after birth
T-cells DON’T produce antibodies
4 types
1. Helper T-cells Suppressor T-cells
2. Killer T-cells Memory T-cells

31. Helper T-cells Recognise Antigens on surface of other WBC
Enlarge, multiply and form a group
Secretes a range of chemicals- Interferons
This stimulates the production of B-cells
HIV infects these helper T-cells & Killer T-cells

32. Killer T-Cells Attack & destroy abnormal body cells
Virus infected or cancer cells (have antigens)
Killer cells are triggered by helper t-cells
They release protein called Perforin
Forms pores in membrane of target cell
This allows water to flow in, target cells swells and bursts.
Process is called Lysis
Killer T-cells said to be Cytotoxic

33. Suppressor T-Cells Stimulated to grow by specific antigens Grow slowly
Activated after antigen has been destroyed
They inhibit B-cells, Helper T-cells and killer T-cells
This controls the immune response

34. Memory T-Cells Can survive a long time –life
Some stimulate memory B-cells to produce antibodies later in life
May trigger Killer T-cells
Responsible for life long immunity

35. THE IMMUNE RESPONSE