How do our bodies resist infection?
Read this information and then do the questions on the next page.
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There are natural barriers to
reduce the risk of harmful microorganisms entering the body (the skin,
chemicals in tears, sweat and stomach acid).
In suitable conditions (such
as inside the body) these microorganisms can reproduce rapidly.
Symptoms of a disease are
caused by damage done to cells by the microorganisms or the poisons (toxins)
they produce.
Our bodies have immune systems
to defend themselves against the invading microorganisms. The immune system
uses antigens on microorganisms to recognise them.
White blood cells can destroy
microorganisms by engulfing and digesting them, or by producing antibodies.
A different antibody is needed
to recognise each different type of microorganism because each one has a
different antigen.
Once the body has made the
antibody to recognise a particular microorganism it can make that antibody
again very quickly, protecting against that particular microorganism. |