What is Immunity (medical)?
'''Immunity''' is the ability of the body to defend itself from 'foreign bodies'. This means rejecting [[infection]]s, clearing up dust which gets in the [[lung]]s, and killing [[cancer]] cells. Immunity is of two types. [[Innate immunity]] protects the host against [[infection]], but has no 'memory', and so gives no long-term immunity. The second type is [[adaptive immunity]], which does have a kind of 'memory'. It does give long-term protection against specific [[pathogen]]s. All [[animal]]s, [[plant]]s and [[fungi]] have some innate immunity. [[Vertebrate]]s also have adaptive immunity. People can be immunised from some diseases by having a vaccination ([[injection]] of some dead or weakened [[virus]], or [[bacteria]] that causes the disease). [[Vaccination]] builds on the natural immune system to make a person resist certain [[disease]]s. By doing so, the body reacts more quickly to fight the virus/bacteria when it comes. ==History of immunology== [[Immunology]] is a science that examines the structure and function of the immune system. The earliest known mention of immunity was during the [[plague of Athens]] in 430 BC. [[Thucydides]] noted that people who had recovered from a previous bout of the disease could nurse the sick without contracting the illness a second time.<ref>{{cite journal |author=Retief FP, Cilliers L |title=The epidemic of Athens, 430-426 BC |journal=South African Medical Journal |volume=88 |issue=1 |pages=50–3 |date=January 1998 |pmid=9539938}}</ref> In the 18th century, [[Pierre Louis Maupertuis|Pierre-Louis de Maupertuis]] made experiments with [[scorpion]] [[Venom (poison)|venom]] and observed that certain dogs and [[mice]] were immune to this venom.<ref>{{cite journal |author=Ostoya P |title=Maupertuis et la biologie |journal=Revue d'histoire des sciences et de leurs applications |year=1954 |volume=7 |issue=1 |pages=60–78 |url=http://www.persee.fr/web/revues/home/prescript/article/rhs_0048-7996_1954_num_7_1_3379 |doi=10.3406/rhs.1954.3379}}</ref> This and other observation