Immunization 284029 224204795 2008-07-07T20:11:35Z 141.30.219.19 /* Active immunization */ [[Image:Poliodrops.jpg|right|thumb|A child being immunized against [[polio]].]] :''For financial immunization, see [[Immunization (finance)]].'' '''Immunization''', or '''immunisation''', is the process by which an individual's [[immune system]] becomes fortified against an agent (known as the [[antigen|immunogen]]). When the human immune system is exposed to [[molecule]]s that are foreign to the body (''non-self''), it will orchestrate an immune response, but it can also develop the ability to quickly respond to a subsequent encounter (through immunological memory). This is a function of the [[adaptive immune system]]. Therefore, by exposing an individual to an immunogen in a controlled way, their body can learn to protect itself: this is called active immunisation. The most important elements of the immune system that are improved by immunisation are the [[B cell]]s (and the [[Antibody|antibodies]] they produce) and [[T cell]]s. [[Memory B cell]] and [[memory T cells]] are responsible for a swift response to a second encounter with a foreign molecule. Passive immunization is when these elements are introduced directly into the body, instead of when the body itself has to make these elements. Immunisation can be done through various techniques, most commonly '''[[vaccination]]'''. Vaccines against [[microorganism]]s that cause [[disease]]s can prepare the body's immune system, thus helping to fight or prevent an [[infection]]. The fact that [[mutation]]s can cause [[cancer]] [[cell]]s to produce proteins or other molecules that are unknown to the body forms the theoretical basis for therapeutic [[cancer vaccine]]s. Other molecules can be used for immunisation as well, for example in experimental vaccines against [[nicotine]] ([[NicVAX]]) or the hormone [[ghrelin]] (in experiments to create an obesity vaccine). ==Passive and active immunization== Immunisation can be achieved in an active or passive fashion: vaccination is an active form of immunization. ===Active immunization=== :''Main article: [[Active immunity]]'' Active immunisation entails the introduction of a foreign molecule into the body, which causes the body itself to generate immunity against the target. This immunity comes from the T cells and the B cells with their antibodies. Active immunization can occur naturally when a person comes in contact with, for example, a microbe. If the person has not yet come into contact with the [[microbe]] and has no pre-made antibodies for defense (like in passive immunization), the person can become immunized. The immune system will eventually create antibodies and other defenses against the microbe. The next time, the immune response against this microbe can be very efficient; this is the case in many of the childhood infections that a person only contracts once, but then is immune. Artificial active immunization is where the microbe, or parts of it, are injected into the person before they are able to take it in naturally. If whole microbes are used, they are pre-treated, so that they will not harm the injected person as the naturally occurring microbe would. Depending on the type of disease, this technique also works with dead microbes, parts of the microbe, or treated [[toxins]] from the microbe. ===Passive immunization=== :''Main article: [[Passive immunity]]'' Passive immunization is where pre-made elements of the immune system are transferred to a person, and the body doesn't have to create these elements itself. Currently, [[antibodies]] can be used for passive immunization. This method of immunization begins to work very quickly, but it is short lasting, because the antibodies are naturally broken down, and if there are no B cells to produce more antibodies, they will disappear. Passive immunization can be naturally acquired when [[antibodies]] are being transferred from mother to [[fetus]] during [[pregnancy]], to help protect the fetus before and shortly after birth. Artificial passive immunization is normally given by [[injection]] and is used if there has been a recent outbreak of a particular disease or as an emergency treatment to poisons (for example, for [[tetanus]]). The antibodies can be produced in animals or ''[[in vitro]]''. ==External links== * [http://www.immunizationinfo.org National Network for Immunization Information (NNii)] * [http://www.cdc.gov/nip Centers for Disease Control National Immunization Program ] {{Vaccines}} [[Category:Immunology]] [[Category:Immune system]] [[Category:Vaccination]] [[cs:Imunizace]] [[de:Immunisierung]] [[eo:Imunigo]] [[hu:Védőoltás]] [[pt:Imunização]] [[simple:Immunization]] [[sr:Имунизација]]