1. The Human Defence System

2. Human defence system
How do we protect ourselves?

3. Teacher slide
How do we protect ourselves against foreign bodies that cause disease (pathogens)?
Possible answers:
Antibodies, WBC, immune system
Vaccines
Antibiotics / drugs

4. How do I stop you?
How do I get in?

5. Teacher slide
How does the baterica / virus / foreign body get into our bodies?(and what do we have to stop it)
Through:
Skin: physical barrier & sebaceous glands - oil
Cuts / wounds: clots / scabs
Eyes : tears lysozyme enzyme dissolves cell walls
Mouth: lysozyme in saliva
Nose: cilia, mucous to trap bugs
Stomach: hydrochloric acid
Vagina – lactic acid bacteria prevents growth of other bacteria
Called first line of general defence

6. “We’re in… now what?”

7. Teacher slide Once a pathogen gets in, what happens then?
White blood cells eat them up (phagocytes)
Some phagocytes are very big and live a long time looking for pathogens – Macrophages
Defence Proteins
(Complement) causes pathogens to burst
Interferons – prevents viral multiplication

8. Teacher slide Once a pathogen gets in, what happens then? Inflammation
Cells get infected they release chemical call histamine
Blood capillaries open wider + become porous
Causes swelling, redness heat and pain
Inflammation in whole body and inc temp = fever

9. Human Defence System General Defence System Non-specific
Skin, Mucous Membranes & secretions
(physical barriers)
White blood cells & chemicals to destroy any pathogens that penetrate the body
(biochemically inside body)

10. Human Defence System Specific Defence System (Immune System)
Attacks specific pathogens by:
Producing Antibodies
Killing infected cells

11. 1st line of General Defence System
Skin
Physical barrier that prevents pathogens getting through
Clotting
If skin is broken, blood clotting prevents entry of pathogens

12. 1st line of General Defence System
Lysozyme
Enzyme found in sweat, tears & saliva
Attacks & dissolves bacterial cell walls
Sebaceous Glands
Chemicals that kill bacteria are released in the oil

13. 1st line of General Defence System
Mucous
Lines many body systems
Traps pathogens
Acid
HCl in stomach kills many pathogens

14. 1st line of General Defence System
Cilia
Lines respiratory system
Beat and move mucous to stomach
Coughing helps to move this mucous
Beneficial Bacteria
Lactic acid
Prevents growth of pathogens

15. Recap Quiz What are Foreign bodies/cells that cause disease ?
Pathogens
Is the general defence system specific or non-specific?
Non-specific
What is the first line of defence of the general defence system?
Skin, mucous membranes & secretions

16. Recap Quiz How does the specific defence system work?
By producing antibodies & killing infected cells
Where would you find lysozyme?
Tears, sweat, & saliva
What does it do?
Dissolve cells walls of bacteria

17. 2nd line of general defence
White blood cells
Defence Proteins
Inflammation

18. 2nd line of general defence
WBC
Pathogen invades cell
Releases chemicals
Attracts WBC
WBC Phagocytes engulf bacteria

19. 2nd line of general defence

20. 2nd line of general defence
Very large phagocytes = Macrophages
Long life
Some move around body looking for pathogens
Some stay in fixed location (e.g. spleen, lymph nodes, tonsils, adenoids, appendix)

21. 2nd line of general defence
Defence proteins
Complement Interferon
(set of 20 proteins) (set of defence proteins)

22. 2nd line of general defence
Complement
Infection
Activates Complement proteins
Chain reaction
Bursting of viruses & pathogens

23. 2nd line of general defence
Interferon
Infected body cell
Produces interferon
Stimulates cells to
Prevent viral multiplication
Spreads to other cells

24. 2nd line of general defence
Infected cell
Releases histamine
Capillaries dilate
Swelling /redness/ heat /pain
Fight infection
Inflammation
WBC

25. 2nd line of general defence
Inflammation occurs over whole body
Causes increased body temperature
Called fever
This interferes with the reproduction of viruses and bacteria

26. Specific Defence System (Immune System)
Attacks SPECFIC pathogens
Produces Antibodies
WBC kill infected cells

27. Specific Defence System (Immune System)
Bone Marrow
White blood cells
Lymphocytes Monocytes
Move to blood vessels
Lymph vessels, lymph nodes,
Spleen, thymus gland

28. Monocytes Monocytes Macrophages Digests pathogens Display antigens
Antibody production

29. Macrophages
Antigens from pathogen
Macrophage

30. Attack body cells which contain antigens on surface of cell
Lymphocytes
Attack body cells which contain antigens on surface of cell or
Attacks cancer cells
Produces ANTIBODIES

31. Recap What are the components of the 2nd line of general defence?
White blood cells
Defence Proteins
Inflammation

32. Recap How do the white blood cells work?
Attracted by chemicals to the infected cell and engulf bacteria
What are the defence proteins?
Complement
Interferons

33. Recap What do the complement proteins do?
They cause a chain reaction which bursts cells
What do the interferons do?
They prevent viral multiplication
How does inflammation work?
Produces heat, swelling, pain and redness and interferes with pathogen reproduction

34. Recap How does the specific defence system work?
It produces antibodies & WBC kill infected cells
What are the WBC involved?
Lymphocytes & Monocytes

35. Recap How do the monocytes work?
They become macrophages and digest pathogens
How do the lymphocytes work?
They attack infected cells and they produce antiboides.

36. Objectives
Understand the antigen – antibody response

37. Antigens Antibody generating
Foreign molecule stimulates production of antibodies
Teacher notes:
Antigens include molecules from the coats of viruses and cell walls of bacteria, fungi and other micro organisms
Antigens are also found in parts of foreign cells e.g. pollen grains
Does anybody know what happens when the above scenario takes place?
Allergic reaction
Other places you will find antigens are on incompatible blood transfusions, transplanted organs and cancer cells

38. Antibody
Is a protein produced by white blood cells (called lymphcytes) in response to an antigen

39. Antibodies Part of family of proteins called IMMUNOGLOBULINS
Pathogens can display large number of antigens on its surface
Many similar shaped antibodies bind to antigens on surface of pathogen

40. 1. Antibodies attach to antigens
Stops pathogen entering new cell
2. Cause pathogens to clump together
Allows phagocytes to destroy pathogens
3. Trigger Complement system
Pathogenic cells are burst
The antigen – antibody reaction is highly specific
i.e. there is a precise fit between antibody and antigen
Each antigen stimulates the production of only one antibody

41. How antibodies dispose of antigens
Antibodies attach to antigens
Stops pathogen entering new cell
Cause pathogens to clump together
Allows phagocytes to destroy pathogens
Trigger Complement system
Pathogenic cells are burst

42. How long does immunity last?
2nd contact – 5 days
1st contact – 14 days
Teacher notes:
Ask students how long immunity lasts?
e.g. if you have the measles as a child and are exposed to them as an adult will you get the measles again? Why?
After an infection is overcome, antibody producing lymphocytes stay in the body for a long time.
If you are exposed to the same antigen again, the lymphocytes can quickly produce large amount of the specific antibodies
So you won’t suffer from the same infection 2nd time round
On first contact with a pathogen it takes up to 14 days to produce the max number of antibodies
Second time exposed to the same pathogen (antigen) it only takes 5 days to produce antibodies in large numbers

43. What about colds & flus? Why do we keep getting colds and flus?
Many different forms
Each have different antigens
Mutate constantly

44. Problems with antigen-antibody reaction
Reaction is disabled in people who have AIDS
Can produce antibody against own body
Allergies
Teacher notes:
The importance of antibody-allergen reaction is illustrated in people who have AIDS as it is disabled in these people. I.e. they can’t fight infection
Sometimes our own bodies produce antibodies against our own tissues e.g. rheumatoid arthritis – joints are attacked or MS where the myelin sheath of nerve cells is attacked
Allergies occur when our bodies produce antibodies against materials which should not be antigenic e.g. pollen, food, dust mites etc
Therefore allergies are said to be inappropriate immune responses

45. Recap What is an antigen?
Foreign molecule stimulates production of antibodies
What is an antibody?
Is a protein produced by white blood cells (called lymphcytes) in response to an antigen

46. Recap
What is the name of the family of proteins that antibodies are from?
Immunoglobulins
How do antibodies dispose of antigens?
Antibodies attach to antigens
Stops pathogen entering new cell
Cause pathogens to clump together
Allows phagocytes to destroy pathogens
Trigger Complement system
Pathogenic cells are burst

47. Recap How long does immunity last?
After an infection is overcome, antibody producing lymphocytes stay in the body for a long time.
Name 3 problems associated with antibody-antigen interaction
Disabled in AIDS patients
Can cause autoimmune disorders (RA & MS)
Can cause allergies (inappropriate immune responses)

48. Induced Immunity
Is the ability to resist disease caused by specific pathogens by the production of antibodies
2 types of induced immunity
Active Immunity
Passive Immunity

49. Active immunity
Production of a person’s own antibodies in response to antigens that enter body
Develops after person is infected by virus or bacterium or vaccination
Long-lasting as lumphocytes that make the antibody have a long life

50. Active immunity Natural Artificial Active Active Immunity Immunity
Teacher notes:
Ask what do you think this means?
Natural is the normal way ie we get infected with a pathogen in the normal way and artificial is when we are immunised

51. Natural Active Immunity
Occurs when we get infected in normal way
e.g. when we get infected with cold / flu/ chicken pox etc…
We develop natural immunity by producing antibodies

52. Artificial Active Immunity
Occurs when we are immunised i.e. get a vaccine
A vaccine is a non disease causing dose of a pathogen (or toxin) which triggers the production of antibodies

53. What is a vaccine? Can contain pathogens that are killed
May be only the outer wall / coat of pathogen (this is where the antigens are)
Sometimes it is a bacterial toxin
Sometimes it is a genetically engineered antigen (no risk of infection)

54. Develops antibodies to pathogen
How does a vaccine work?
Receives the vaccine
Develops antibodies to pathogen
No symptoms infection
Life long immunity
Notes:
The ability to make these antibodies persists in the body conferring life long immunity

55. History of vaccines Teacher notes: Ask if anyone knows who this is?
Edward Jenner
The first vaccine was given by EJ in 1796
Jenner had learned that milk maids who had suffered cow pox ( a non fatal viral infection) were resistant to small pox (fatal usually)
Jenner inoculated cowpox virus into a young boy.
6 weeks later he inoculated the young boy with small pox
Luckily the boy survived
Cowpox and smallpox have similar antigens, once the boy had produced antibodies to the cowpox he was immune to smallpox
Vacca is the latin for cow and hence Vaccine
Smallpox was eradicated in 1976 and now exists only in a laboratory in the USA and Russia

56. Vaccinations What types can you think of? TB, Diptheria Whooping cough
MMR
Flu
Meningitis

57. Passive immunity Natural Artificial Passive Passive Immunity Immunity
Teacher notes:
Ask what do you think this means?
Natural passive immunity occurs when a mother passes on immunity either across the placenta or through breast milk
artificial Passive immunity is when a person gets an injection of antibodies from another source

58. Natural Passive Immunity
Child gets antibodies from mother
Through the placenta
Breast milk
How long?
Only lasts for first few months of life

59. Artificial Passive Immunity
When a person is given an injection containing antibodies from another organism
Antibodies act fast to control disease
Do not last long – are broken down
E.g. anti-tetanus injection
Notes:
In anti-tetanus injection the antibodies are are extracted from blood of horses with tetanus.
The horse antibodies are given to an infected person.

60. Recap What are the 2 types of induced immunity called?
Active and Passive
What is Active immunity?
Antibodies produced in person’s own body
2 types of active immunity what are they?
Natural and artificial
Notes:
In anti-tetanus injection the antibodies are are extracted from blood of horses with tetanus.
The horse antibodies are given to an infected person.

61. Recap What is natural active immunity?
When pathogens enter the body naturally and you produce antibodies in response
What is artificial active immunity?
When a pathogen is introduced artificially like vaccine
Notes:
In anti-tetanus injection the antibodies are are extracted from blood of horses with tetanus.
The horse antibodies are given to an infected person.

62. Recap What is Passive immunity?
Antibodies from another organism enter a person’s body
There are 2 types, what are they?
Natural passive immunity
Artificial passive immunity
Notes:
In anti-tetanus injection the antibodies are are extracted from blood of horses with tetanus.
The horse antibodies are given to an infected person.

63. Recap What is natural passive immunity?
Antibodies enter a body through natural means
What are natural means?
Breast milk
Through the placenta
Notes:
In anti-tetanus injection the antibodies are are extracted from blood of horses with tetanus.
The horse antibodies are given to an infected person.

64. Recap What is natural artificial immunity?
Antibodies are injected into a person
An example?
Anti-tetanus injections
Notes:
In anti-tetanus injection the antibodies are are extracted from blood of horses with tetanus.
The horse antibodies are given to an infected person.

65. Lymphocytes What are lymphocytes? White blood cells
Where are they formed?
Bone Marrow
What is their structure?
Large round nucleus and very little cytoplasm

66. Lymphocytes White blood cells Formed in the Bone Marrow
their structure is Large round nucleus and very little cytoplasm
2 types
B-lymphocytes – mature in Bone marrow
T-lymphocytes – mature in Thymus gland

67. B-Lymphocytes / B-cells
Mature in bone marrow
Move to lymphatic tissue especially spleen and lymph nodes
Millions of different types of B cells
Each B-cell recognises only one antigen & only produces one type of antibody

68. B-cells B-cell comes into contact with its specific antigen
It divides to produce identical B cells
These B-cells are called Plasma cells
These produce large numbers of the required antibody
Plasma cells only live a few days but produce 2000 antibody molecules per second

69. B - Cells

70. B-cells How do antibodies inactivate antigens?
They attach to them and this allows the cells carrying the antigen to be disposed of by phagocytes or by activating complement (which bursts cells)

71. B-cells Most die off once the infection has been overcome
Some remain alive for years
Surviving B-cells allow the body to respond if the same antigen enters the body
This secondary response is more effective ?
Why

72. B-cells This secondary response is more effective ?
Produces antibodies in response to much smaller amounts of antigen
Produces antibodies much faster (5 days as opposed to 14 days)
Produces much greater number of antibodies
These factors prevent us from being infected more than once by the same pathogen

73. T-cells Move from bone marrow to thymus where they become activated
Important in early months and years of life
Do not produce antibodies
Act against viruses and bacteria

74. T-cells 4 types Helper T-cells Killer T-cells Supressor T-cells
Memory T-cells

75. 1. Helper T-cells Recognise antigens on surface of other cells
Antigens activate helper T-cells
T-cells multiply and enlarge and form a group of helper T-cells

76. 1. Helper T-cells
Group secretes chemicals e.g. interferons (which prevent viral replication)
Chemicals stimulate production & activation of antibody producing B-cells
Also stimulates Killer T-cells to reproduce
HIV infects helper T-cells (VIDEO)

77. 2. Killer T-cells Attack abnormal body cells
i.e. virus infected or cancer cells
Stimulated by Helper T-cells
Release Perforin
Perforin makes pores in the membrane which causes cells to burst
Cytotoxic cells

78. Killer T-cells

79. 3. Suppressor T-cells Growth is stimulate by specific antigens
Grow more slowly than other T-cells
Become active once pathogen is destroyed
Inhibit B-cells and other T-cells
Control and stop immune response

80. 4. Memory T-cells Survive for a long time Lifetime
Stimulate B-cells to produce antibodies
Trigger production of killer T-cells

81. Recap What are lymphocytes? White blood cells Where are they formed?
Bone Marrow
What is their structure?
Large round nucleus and very little cytoplasm

82. Recap Where do B-cells mature Bone marrow Where do T-cells mature?
Thymus
A number of identical B-cells are called?
Plasma cells
What do they do?
Produce antibodies

83. Recap Describe the secondary response?
This secondary response is more effective ?
Produces antibodies in response to much smaller amounts of antigen
Produces antibodies much faster (5 days as opposed to 14 days)
Produces much greater number of antibodies

84. Recap How many types of t-cells? 4 types Helper T-cells Killer T-cells
Supressor T-cells
Memory T-cells
What does each one do?
Helper T – produce chemicals that stimulate b-cells to produce antibodies

85. Recap
Killer T cells?
Produce perforin which causes abnormal body cells to burst
Suppressor t cells
Turn off immune system
Memory t cells
Survive a long time to trigger immunity to the same antigen later in life.

86. Recap