| Immunity (medical) |
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Specific, or adaptive immunity is often sub-divided into two major types depending on how the immunity was introduced. '''Natural immunity''' occurs through contact with a disease causing agent, when the contact was not deliberate, whereas '''artificial immunity''' develops only through Deliberate Actions . Both natural and artificial immunity can be further subdivided, depending on the amount of time the protection lasts. '''Passive immunity''' is short lived, and usually lasts only a few months, whereas protection via '''active immunity''' lasts much longer, and is sometimes life-long. The diagram below summarizes these divisions of immunity. A further subdivision of adaptive immunity is characterized by the cells involved; Humoral Immunity is the aspect of immunity that is mediated by secreted antibodies, whereas the protection provided by Cell Mediated Immunity involves T-lymphocytes alone. Humoral immunity is active when the organism generates it’s own antibodies, and passive when antibodies are transferred between individuals. Similarly, cell mediated immunity is active when the organisms’ own T-cells are stimulated and passive when T cells come from another organism. HISTORY OF THEORIES OF IMMUNITY Epidemic of the nineteenth century.]] The concept of immunity has intrigued mankind for thousands of years. The prehistoric view of disease was that it was caused by supernatural forces, and that illness was a form of , which held that diseases such as Cholera or the Black Plague were caused by a Miasma , a noxious form of "bad air". If someone were exposed to the miasma, they could get the disease. The modern word “immunity” derives from the ” written around 60 B.C. by the poet Marcus Annaeus Lucanus to describe a North African tribe’s resistance to Snake Venom . The first clinical description of immunity which arose from a specific disease causing organism is probably ''Kitab fi al-jadari wa-al-hasbah'' (''A Treatise on Smallpox and Measles'', translated 1848 A "al-Razi." 2003 The Columbia Electronic Encyclopedia, Sixth Edition. Columbia University Press (from Answers.com, 2006.)) written by the Islamic physician Al-Razi in the 9th century. In the treatise, Al Razi describes the clinical presentation of smallpox and measles and goes on to indicate that that exposure to these specific agents confers lasting immunity (although he does not use this term). However, it was with Louis Pasteur ’s Germ Theory Of Disease that the fledgling science of Immunology began to explain how bacteria caused disease, and how, following infection, the human body gained the ability to resist further insults. |
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