The Human Defence System
Human defence system
• How do we protect
ourselves?
How do I
get in?
How do I
stop
you?
“We’re in…
now what?”
Human Defence System
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•
General Defence System
Non-specific
1. Skin, Mucous Membranes & secretions
(physical barriers)
2. White blood cells & chemicals to destroy
any pathogens that penetrate the body
(biochemically inside body)
Human Defence System
•
•
Specific Defence System (Immune
System)
Attacks specific pathogens by:
1. Producing Antibodies
2. Killing infected cells
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
1st line of General Defence System
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•
Lysozyme
–
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Enzyme found in sweat, tears & saliva
Attacks & dissolves bacterial cell walls
Sebaceous Glands
–
Chemicals that kill bacteria are released
in the oil
1st line of General Defence System
•
Mucous
–
–
•
Lines many body systems
Traps pathogens
Acid
–
HCl in stomach kills many pathogens
1st line of General Defence System
•
Cilia
–
–
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•
Lines respiratory system
Beat and move mucous to stomach
Coughing helps to move this mucous
Beneficial Bacteria
–
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Lactic acid
Prevents growth of pathogens
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
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
2nd line of general defence
• White blood cells
• Defence Proteins
• Inflammation
2nd line of general defence
Pathogen invades cell
Releases chemicals
Attracts WBC
WBC Phagocytes engulf bacteria
2nd line of general defence
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)
2nd line of general defence
Defence proteins
Complement
(set of 20 proteins)
Interferon
(set of defence
proteins)
2nd line of general defence
Infection
Activates Complement proteins
Chain reaction
Bursting of viruses & pathogens
2nd line of general defence
Infected body cell
Produces interferon
Spreads to other cells
Stimulates cells to
Prevent viral multiplication
2nd line of general defence
Infected cell
Releases histamine
Capillaries dilate
Swelling /redness/ heat /pain
WBC
Fight infection
2nd line of general defence
•
•
•
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Inflammation occurs over whole body
Causes increased body temperature
Called fever
This interferes with the reproduction
of viruses and bacteria
Specific Defence System
(Immune System)
Attacks SPECFIC pathogens
1. Produces Antibodies
2. WBC kill infected cells
Specific Defence System
(Immune System)
Bone Marrow
White blood cells
Lymphocytes
Monocytes
Move to blood vessels
Lymph vessels, lymph nodes,
Spleen, thymus gland
Monocytes
Monocytes
Macrophages
Digests pathogens
Display antigens
Antibody production
Macrophages
Antigens
from
pathogen
Macrophage
Lymphocytes
Attack body cells
which contain
antigens on
surface of cell
or
Attacks cancer
cells
Produces
ANTIBODIES
Recap
• What are the components of the 2nd line
of general defence?
• White blood cells
• Defence Proteins
• Inflammation
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
Recap
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•
•
•
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
Recap
• How does the specific defence system
work?
• It produces antibodies & WBC kill
infected cells
• What are the WBC involved?
• Lymphocytes & Monocytes
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.
Objectives
• Understand the antigen – antibody
response
Antigens
• Antibody generating
• Foreign molecule
stimulates production
of antibodies
Antibody
• Is a protein
produced by white
blood cells (called
lymphcytes) in
response to an
antigen
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
How antibodies dispose of
antigens
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
How long does immunity last?
2nd contact – 5 days
1st contact – 14 days
What about colds & flus?
• Why do we keep getting
colds and flus?
• Many different forms
• Each have different
antigens
• Mutate constantly
Problems with antigen-antibody
reaction
• Reaction is disabled in people who have
AIDS
• Can produce antibody against own body
• Allergies
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
Recap
•
•
What is the name of the family of proteins that
antibodies are from?
Immunoglobulins
•
1.
How do antibodies dispose of antigens?
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
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 antibodyantigen interaction
– Disabled in AIDS patients
– Can cause autoimmune disorders (RA & MS)
– Can cause allergies (inappropriate immune
responses)
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
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
Active immunity
Natural
Active
Immunity
Artificial
Active
Immunity
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
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
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)
How does a vaccine work?
Receives the vaccine
Develops antibodies to pathogen
No symptoms infection
Life long immunity
History of vaccines
Vaccinations
• What types can you
think of?
• TB, Diptheria
• Whooping cough
• MMR
• Flu
• Meningitis
Passive immunity
Natural
Passive
Immunity
Artificial
Passive
Immunity
Natural Passive Immunity
• Child gets antibodies from mother
– Through the placenta
– Breast milk
• How long?
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
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
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
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
Recap
• What is natural passive immunity?
• Antibodies enter a body through natural
means
• What are natural means?
• Breast milk
• Through the placenta
Recap
• What is natural artificial immunity?
• Antibodies are injected into a person
• An example?
• Anti-tetanus injections
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
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
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
B - Cells
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)
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
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
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
T-cells
• 4 types
Helper T-cells
Killer T-cells
Supressor T-cells
Memory T-cells
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
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)
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
Killer T-cells
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
4. Memory T-cells
• Survive for a long time
• Lifetime
• Stimulate B-cells to produce antibodies
• Trigger production of killer T-cells
Recap
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What are lymphocytes?
White blood cells
Where are they formed?
Bone Marrow
What is their structure?
Large round nucleus and very little cytoplasm
Recap
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•
•
•
Where do B-cells mature
Bone marrow
Where do T-cells mature?
Thymus
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A number of identical B-cells are called?
Plasma cells
What do they do?
Produce antibodies
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
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
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.
Recap