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Pathogens are micro-organisms that cause infectious
disease. Bacteria and viruses are the main pathogens.
· The Immune System is body's defence against infection
and disease
· Antibodies and Antitoxins are not living cells, they are
specialised proteins
· Antigens are chemicals that are foreign to the body,
they can be found in pathogens.
· An Antibody is a protein which chemically fits a certain
antigen…read more

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Bacteria
· Single celled micro-organism
· Multiply rapidly in favourable conditions
· They release toxins inside our body, this
makes us feel ill.
· Can be destroyed by antibiotics.…read more

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Viruses
· A lot smaller than bacteria
· They can only reproduce inside host cells.
When inside a sell, they reproduce till the
cell bursts and then they go in to the
bloodstream…read more

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First Line of Defence
Most pathogens can only infect when in side the body. Our
body has created many different ways to stop them getting
in side. The is called Passive Immunity.
· Chemicals in Tears and Sweat
· Skin ­ it is a physical barrier which most pathogens can
not penetrate and the sebaceous glands just under the
skins surface produces oil which also helps to kill the
microbes.
· Stomach Acid ­ the stomach contains hydrochloric acid
which destroys micro-organisms that we might have
swallowed with food or drink before they make us ill. For
example they prevent food poisoning that can be caused
by salmonella and other harmful bacteria.…read more

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Second line of Defence
If the microbes are not destroyed by the previous defence
methods mentioned, the body has to use a more advanced
way for destroying it. This is called Active Immunity. The
white blood cells are important for this to happen.
White blood cells can:
· ingest pathogens and destroy them
· produce antibodies to destroy pathogens
· produce antitoxins that neutralise the toxins released by
pathogens…read more

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