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biology 0610printed 127 · PDF 127
328 pagesrevision 46933
printed 127 · PDF 127
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● Every call including pathogens have proteins called antigens
extending from their cell membranes
● Different cells have different antigens; thus lymphocytes (a type
of white blood cells) can recognise foreign antigens and make
antibodies which have a complementary shape to the antigen
● These antibodies attach to antigens and causes pathogens to
agglutinate (clump together) and restrict their motion.
● Meanwhile phagocytes (another type of white blood cells) engulf
and destroy the agglutinated pathogens and destroy them. They do
this through the process of phagocytosis
Active Immunity
● Active immunity is the defence against a pathogen by antibody
production in the body. This type of immunity can be achieved after
an infection by a pathogen, or through vaccination. This type of
immunity is long term yet slow acting.
● Infection:
o In the case of an infection, it might take the lymphocytes to take
a few days to react and then form antibodies.
o After an infection, memory cells can be formed which retain the
instructions for making the specific type of antibodies, so that if
there is a re-infection, the body can quickly produce antibodies
before the person can become sick
o This makes a person immune to the disease, unless the
pathogen mutates
● Vaccination:
o Vaccinations can give protection against certain diseases without
being directly exposed to harmful pathogen
o Vaccines are essentially dead or very weakened forms of specific
pathogens, containing the specific antigens
o They are too weak to cause illness but an immune response
does occur and as a result antibodies and eventually memory cells
are produced.