The immune system is a set of mechanisms that protect an organism from
infection by identifying and killing pathogens. This task is extremely
difficult, since pathogens range from viruses to parasitic worms and
these diverse threats must be detected with absolute specificity
amongst normal cells and tissues. Pathogens are also constantly
evolving new ways to avoid detection by the immune system and
successfully infect their hosts. To meet this challenge, multiple
mechanisms have evolved to recognize and neutralize pathogens. The
immune systems of vertebrates such as humans consist of many types of
proteins, cells, organs, and tissues, which interact in an elaborate
and dynamic network. As part of this more complex immune response, the
vertebrate system adapts over time to recognize particular pathogens
more efficiently. The adaptation process creates immunological
memories and allows even more effective protection during future
encounters with these pathogens. This process of acquired immunity is
the basis of vaccination.
Read the rest of this article:
http://en.wikipedia.org/wiki/Immune_system
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Today's selected anniversaries:
1700:
Sweden introduced its own Swedish calendar in an attempt to reform
into the Gregorian calendar.
(
http://en.wikipedia.org/wiki/Swedish_calendar)
1872:
Yellowstone National Park, the first national park in the world, was
established.
(
http://en.wikipedia.org/wiki/Yellowstone_National_Park)
1896:
Ethiopia won the decisive Battle of Adowa over Italy, ending the First
Italo-Abyssinian War.
(
http://en.wikipedia.org/wiki/Battle_of_Adowa)
1919:
Korea under Japanese rule: The Samil Movement began with numerous
peaceful protests in Korea, but was brutally suppressed by the
Japanese police and army.
(
http://en.wikipedia.org/wiki/March_1st_Movement)
1954:
The 15-megaton hydrogen bomb Castle Bravo was detonated on Bikini
Atoll in the Pacific Ocean, resulting in one of the worst cases of
radioactive contamination ever caused by nuclear testing.
(
http://en.wikipedia.org/wiki/Castle_Bravo)
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Wikiquote of the day:
We should not be simply fighting evil in the name of good, but
struggling against the certainties of people who claim always to know
where good and evil are to be found. -- Tzvetan Todorov
(
http://en.wikiquote.org/wiki/Tzvetan_Todorov)