How do our bodies resist infection?

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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.