Transcript The Human Defence System - Ms Curran`s Leaving Certificate Biology

The Human Defence
System
What I need to know from this chapter
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General defence system
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skin, mucous membrane of the breathing system,
reproductive and digestive tracts. Phagocytic white
blood cells
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Specific defence system
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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.
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General Defence System
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Non specific
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Acts against all pathogens
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Consists of two parts
1st Part of Defence System
Skin
 Mucus
 clotting
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Lysozyme
 Cilia
 Acid
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Sebaceous
gland
 Good bacteria
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2nd Part of the Defence System
Phagocytic white blood cells
 Inflammation
 Defence Proteins/complement system
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Skin
st
(1 Line defence)
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Skin – provides a structural barrier to infection
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Clotting – prevents entry of pathogens
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Lysozyme – Enzyme found in sweat, tears, saliva
- Dissolves cell walls of bacteria
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Sebaceous glands – chemicals to kill bacteria
Respiratory Tract
st
(1 Line defence)
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Respiratory tract lined with mucus
-Traps pathogens
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Respiratory tract has cilia
- Moves mucus back up into the throat
- carries pathogens out
Digestive Tract
st
(1 Line defence)
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Produces mucus
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Produces acid in the stomach
- kills many bacteria
Reproductive tract
st
(1 Line defence)
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Beneficial bacteria in vagina produce lactic
acid – prevents growth of pathogens
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
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Phacocytosis -White Blood Cells
White cell
Germ
“Eating”
germ
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
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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.
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Specific Defence System
(The Immune System)
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Attacks particular pathogens
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Produces antibodies which kill pathogens
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Produces white blood cells
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
Antibodies
An antigen are chemicals
that are on the surface of
a pathogen
An antibody produced by
lymphocytes in response
to an antigen
Antibodies
What antibodies do
Prevent viruses and bacteria from entering
new host cells
2. Label pathogens to be destroyed by
phagocytes
3. Antibodies can inactivate pathogens by
making them clump together
4. Can trigger the complement system –
This causes pathogen cells to burst
1.
Pathogen Clump
Complement Protein
Antigen Antibody Reaction
Highly specific
 Each antigen stimulates the production of
one antibody
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Why we get flu every year
 Different strain
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Problems
Can be disabled - AIDs
 Body produces antibodies against its own
tissues
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 Rheumatoid
Arthritis
 Multiple Sclerosis
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Allergies
Duration of Immunity
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After infection antibodies remain
1st time an antigen is produced
14 days to produce maximum no. of
antibodies
Subsequent infection – 5 days
Induced Immunity
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Is the ability to resist disease caused by
specific pathogens by the production of
antibodies.
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2 Types of immunity
1. Active
2. Passive
Active Immunity
Production of your own antibodies in response
to antigens.
 Is longer-lasting
 Can be induced naturally or artificially
Natural Active Immunity
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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
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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
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Child gets antibodies from mother
 Either through the placenta or mothers milk
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Artificial Passive Immunity
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Given an injection with antibodies produced by other
organism. i.e. Anti-tetanus injection (from horses)
Advanced Study of Lymphocytes
2 Types (mature in different places)
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B-lymphocytes (B-cells)
–Bone Marrow
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T-lymphocytes (T-cells)
– Thymus Gland
B-Cells
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When matured move from bone marrow to
lymphatic tissue
–Esp. Spleen and Lymph nodes
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There are millions
Each adapted to recognise 1 specific antigen
Produces only 1 type of antibody
B-Cells
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Divides & produces more B-cells (Plasma cells)
on contact with antigen
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Plasma cells -short lived, produce 2000 AB a
second
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Anti-bodies AB inactivate antigen by attaching to
them
Disposed 1. phagocytes
2. Complement system (cells burst)
B-Cells
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Some B-cells remain alive = memory B-cells
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Secondary response is more effective
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Produces antibodies to small amounts of antigen
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Much faster response
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Greater numbers of antibodies
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Active in controlling bacterial infections
T-Cells
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Activated when they move from bone marrow to
Thymus
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Thymus is most active in weeks before & after birth
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T-cells DON’T produce antibodies
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4 types
1. Helper T-cells
2. Killer T-cells
3. Suppressor T-cells
4. Memory T-cells
Helper T-cells
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Recognise Antigens on surface of other WBC
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Enlarge, multiply and form a group
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Secretes a range of chemicals- Interferons
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This stimulates the production of B-cells
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HIV infects these helper T-cells & Killer T-cells
Killer T-Cells
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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
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Suppressor T-Cells
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Stimulated to grow by specific antigens
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Grow slowly
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Activated after antigen has been destroyed
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They inhibit B-cells, Helper T-cells and killer
T-cells
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This controls the immune response
Memory T-Cells
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Can survive a long time –life
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Some stimulate memory B-cells to produce
antibodies later in life
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May trigger Killer T-cells
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Responsible for life long immunity
THE IMMUNE
RESPONSE