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Defending against infectious disease:

Pathogens are microorganisms that cause disease. Pathogens include bacteria and viruses.
Bacteria releases toxins and viruses damage our cells. White blood cells can destroy and ingest
pathogens. They can produce antibodies that destroy pathogens, and antitoxins that neutralise

In a vaccination, pathogens are introduced into…

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The body can protect itself against pathogens in many different ways. The first defence is passive
immunity. This aims to stop pathogens from entering the body. The body's passive immunity
includes, skin, mucus, cilia (respiratory system), acid in the stomach and enzymes (in tears).
Passive immunity is also maternal antibodies…

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lymphocyte reproduces quickly, and makes many copies of the antibody that neutralise the
pathogen. Antibodies neutralise pathogens in a number of ways:

they bind to pathogens and damage or destroy them
they coat pathogens, clumping them together so that they are easily ingested by phagocytes
they bind to the pathogens…

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Bacterial strains can develop resistance to antibiotics. This happens because of natural selection.
In a large population of bacteria, there may be some cells that are not affected by the antibiotic.
These cells survive and reproduce, producing even more bacteria that are not affected by the
antibiotic. MRSA is very…


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