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biology 0610printed 130 · PDF 130
328 pagesrevision 46933
printed 130 · PDF 130
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Passive Immunity
● Passive immunity is a short-term defence against a pathogen by
antibodies acquired from another individual
● Examples of this include breastfeeding and through the
placenta
● Passive immunity is fast acting yet short-term as the body does
not make its own antibodies or memory cells
● In breastfeeding, antibodies pass from mother to infant through
breast milk-this is important to fight off infections while their
immune systems are still developing
Cholera
● Cholera is a disease caused by the bacteria Vibrio Cholera.
This bacterium is transmitted through contaminated water or food
o When these bacteria enter the small intestine, it binds to the
small intestine wall and then produces a toxin
o This toxin causes cells on the intestinal lining to secrete chloride
ions into the lumen (hollow space) of the small intestine.
o These chloride ions decrease the water potential of the lumen as
compared to the blood and thus water flows through osmosis from
the cells into the lumen.
o This causes a large volume of water to be lost from the body as
faeces and is called diarrhoea.
o This also leads to low concentration of Cl ions in the blood and
causes dehydration.