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IMMUNITY
ABBOTTS 2010
INFECTIONS
Are caused by pathogenic Monera [viruses and bacteria] and Protista [Protozoans] and Fungi
An infection is the detrimental colonization of a host organism by a foreign species.
DEFINITION
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PATHOGENS
= disease causing micro-organisms
bacteria virus fungi, protozoa,
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IMMUNE RESPONSE BY PLANTS
Plant pathogens harm plant growth and reproduction Plants have an immune system to defend themselves
against infections
A plant recognizes the shape of the infecting pathogen and the infected cells are stimulated
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IMMUNE RESPONSE IN PLANTS
Produce salicylic acid a plant hormone or signal It is an asprin-like compound
Activate resistance genes which resist the pathogen – e.g. stop viral replication
Self destruct – form an area of dead cells to prevent the infection from spreading
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SYSTEMATIC ACQUIRED RESISTANCE
Salicylic acid moves from the infected site through the phloem to uninfected parts of the plant to activate the immune system to produce defensive compounds to make the entire plant resistant to the pathogen
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FIRST LINES OF DEFENCE
skin prevents entry
tears antibacterial enzymes
saliva antibacterial enzymes
stomach acid low pH kills harmful microbes
mucus linings traps dirt and microbes
“good” gut bacteria out compete bad
Try to prevent the entry of germs
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PATHOGENS
= disease causing micro-organisms
bacteria virus fungi, protozoa,
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SECOND LINES OF DEFENCE
IF GERMS DO GET INTO THE BODY:
Primary response – tries to destroy the germs and prevent them from spreading
Secondary response – if germs do spread, the immune system is activated
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PRIMARY RESPONSE
Tries to destroy the germs and prevent them from spreading by:
Inflammation (if it is a local infection) Fever (raised body temperature)
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INFLAMMATION
Local infection Inflammation is a process
by which the bodies white blood cells protect us from infection and foreign substances such as bacteria and viruses
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SECONDARY RESPONSE/SPECIFIC RESPONSE
If germs do start to spread Immune system becomes involved
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IMMUNITY
The body’s active response to an infection
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THE IMMUNE RESPONSE INVOLVES TWO MAIN MEASURES:
Destruction of the invading germs
Holding a memory of this response
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TWO GROUPS OF WHITE BLOOD CELLS INVOLVED IN THE IMMUNE RESPONSE
LYMPHOCYTES
B LYMPHOCYTES T LYMPHOCYTES
PHAGOCYTES
They are part of a huge army in ourbodiesThere are about one trillion B lymphocytesAnd one trillion T lymphocytesThey are found in the tonsils, lymph glands, spleen and blood
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ANTIGENS
all cells have surface markers called antigens.
body can recognise these as self or non-self (foreign)
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B LYMPHOCYTES
Also called antibody cells
If a germ gets into the body, it is detected by these cells
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HOW B LYMPHOCYTES DESTROY GERMS
Germs have molecules called antigens on their surface
The antigen tells the B lymphocyte that the germ is ‘non-human’ and dangerous
There are countless types of B lymphocytes
Each is able to recognize its own specific antigen
The B lymphocyte replicates rapidly producing lots of identical cells (clones)
These newly formed B lymphocytes produce proteins called antibodies into the blood plasma
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The antibodies combine with the antigens on the surface of the germ
BINDING OF ANTIBODIES AND ANTIGENS
This will destroy or neutralise the germ
Some of the B lymphocytes stay in the lymph glands as memory cells
If they encounter the antigen again, they mount a response very quickly and kill the germ before it can breed
This is the basis of immunity
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HOW ANTIBODIES DESTROY GERMS
DIAGRAM: METHODS OF GERM DESTRUCTION BY ANTIBODIES
Antibodies could: Cause bacterial cells to burst Label germs for phagocytosis Cause germs to clump together
[clumps are easier to ingest by phagocytosis]
Neutralize bacterial toxins
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T LYMPHOCYTES
There are different types of T lymphocytes Each cell has a unique role to play in the
immune response CD4 Cells [helper T cells] Killer T cells
CD4 cells are a type of white blood cell (lymphocyte
Killer T cells
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CD4 CELLS/ HELPER T CELLS
Begin the immune response to infections Without these cells the other cells will not do
anything Body’s ability to fight infections would be very
poor
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KILLER T CELLS/ CYTOTOXIC T CELLS
They attack and destroy:
Cancer cells Cells infected with viruses
and some parasites Transplanted organs
[unless immunosuppressive drugs are given to the patient]
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PHAGOCYTES(CELLS THAT EAT!)
DIAGRAM: Are large lymphocytes
(white blood corpuscles) Can change shape They engulf germs by
phagocytosis [and also dead cells and foreign particles]
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HOW DO PHAGOCYTES DESTROY GERMS
Move around the body looking for germs
Squeeze through gaps in capillary walls and reach any part of the body
When it comes into contact with a germ, it engulfs it and takes the germ into the cell
Germ is digested and killed Process called
phagocytosis
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Phagocytosis of E coli
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DEALING WITH INFECTIONS
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THE END
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