In biology, immunity is a balanced state of multicellular organisms that have adequate biological defenses against infections, diseases, or other undesirable biological invasions, while having adequate tolerance to avoid allergies, and autoimmune diseases.
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Default and adaptive
Immunity is the ability of multicellular organisms to hold harmful microorganisms into it. Immunity involves specific and nonspecific components. Non-specific components act as barriers or eliminators of various pathogens irrespective of their antigenic makeup. Other components of the immune system adapt to any new illness encountered and can produce pathogen-specific immunity.
The immune system may contain innate and adaptive components. The innate system in mammals, for example, is composed of primitive bone marrow cells programmed to recognize foreign substances and react. The adaptive system consists of more advanced lymphatic cells programmed to recognize the self-substance and not react. The reaction to a foreign substance is etymologically described as inflammation, which means burning. Non-reaction to self-substances is described as immunity, which means to be freed or as an immunotolerance. These two components of the immune system create a dynamic biological environment in which "health" can be seen as a physical state in which the immunologically self is spared, and what is foreign is inflammation and immunology eliminated. "Illness" can arise when what is foreign can not be eliminated or what self is not spared.
Congenital immunity, also called native immunity, is based on a constitution of the organism, its genetic makeup, without external stimulation or previous infection. It is divided into two types: (a) Innate innate immunity, resistance to all infections in general. (B) specific innate immunity, resistance to certain types of microorganisms only. As a result, certain races, individuals or breeds in agriculture do not suffer from certain infectious diseases.
Adaptive immunity can be divided depending on how immunity is introduced in 'naturally acquired' by contact with disease-causing agents, while 'artificially acquired immunity' develops through deliberate action such as vaccination. Both the naturally occurring and artificial immunity can be subdivided depending on whether the host builds up the immune itself by the antigen as 'active immunity' and lasts a long, sometimes lifelong time. 'Passive immunity' is obtained by transfer (injection or infusion) of antibodies or T cells activated from the immune host; it's short-lived - it usually lasts only a few months. The diagram below summarizes this immunity division.
Adaptive immunity can also be shared by the type of immune mediator involved; Humoral immunity is an aspect of immunity mediated by secreted antibodies, whereas cell-mediated immunity involves T-lymphocytes only. Humoral immunity is called active when the organism produces antibodies, and is passive when antibodies are transferred between individuals or species. Likewise, immune cells are active cell-mediated when T cells are stimulated, and passive when T cells originate from other organisms.
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History of theory
The concept of immunity has made people interested for thousands of years. The prehistoric view of disease is that supernatural forces cause it, and it is a form of theurgic punishment for "bad deeds" or "bad thoughts" visited on the soul by gods or by one's enemies. Between the time of Hippocrates and the 19th century, when the foundations of the scientific method were laid, the disease was associated with changes or imbalances in one of four humor (blood, mucus, yellow bile or black bile). Also popular before learning that infectious diseases originating from germs/microbes is the poison theory, which states that diseases such as cholera or the Black Plague are caused by toxic, harmful forms of "bad air". If a person is poisoned in a swamp, in the night air, or inhaling the air in a hospital room or ward, they can get sick.
The modern word "immunity" comes from the Latin immunis, which means liberation from military service, tax payments or other public services. The first written description of the concept of immunity may have been made by the Athenians of Thucydides who, in 430 BC, described that when the plague hit Athens: "the sick and the dying are prone to the care of the pity of those who have recovered, because they know the course of the disease and they themselves are free from worries, because no one is attacked for a second time, or not with a fatal result ". The term "immunes", also found in the epic poem "Pharsalia" written around 60 BC. by the poet Marcus Annaeus Lucanus to describe the North African tribal resistance against snake poison.
The first clinical feature of immunity arising from certain disease-causing organisms may be Kitab fi al-jadari wa-al-hasbah ('Treatise on Smallpox and Measles', translated 1848) 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 continues to show that exposure to these special agents gives immortal immunity (although he does not use this term). The first scientist to develop a full immune theory was Ilya Mechnikov after he revealed phagocytosis in 1882. With Louis Pasteur's disease germ theory, the new immunology science began to explain how bacteria cause disease, and how, after infection, the human body gains the ability to withstand more infections continue.
The birth of active immunotherapy may begin with Mithridates VI of Pontus. To induce active immunity to snake, he recommends using a method similar to modern toxoid serum therapy, by drinking the blood of animals that eat poisonous snakes. According to Jean de Maleissye, Mithridates assumes that animals that eat poisonous snakes acquire some detoxifying properties in their bodies, and their blood must contain the attenuated snakes or transformed toxic components of snakes. The actions of those components may strengthen the body against the poison rather than using toxic effects. Mithridates reasoned that, by drinking the blood of these animals, he could obtain the same resilience as the snake poison when the animals ate the snake. Similarly, he attempts to harden himself against the poison and take a lethal daily dose to build tolerance. Mithridates is also said to have formed a 'universal antidote' to protect it from all earthly poisons. For almost 2000 years, toxins are thought to be the direct cause of the disease, and a complex mixture of materials, called Mithridate, was used to cure poisoning during the Renaissance. The latest version of this drug, Theriacum Andromachi, was used well until the 19th century. In 1888 Emile Roux and Alexandre Yersin isolated diphtheria toxins, and after the 1890 discovery by Behring and Kitasato from antitoxin-based immunity to diphtheria and tetanus, antitoxin became the first major success of modern therapeutic immunology.
In Europe, active immune activation appears in an attempt to contain smallpox. Immunization, however, has existed in various forms for at least a thousand years. The earliest use of immunization is unknown, however, around 1000 A.D. The Chinese begin to practice the form of immunization by drying and inhaling the powder from the skin of smallpox lesions. Around the fifteenth century in India, the Ottoman Empire, and east Africa, the practice of inoculation (piercing the skin with powdered ingredients derived from smallpox) became very common. This practice was first introduced to the west in 1721 by Lady Mary Wortley Montagu. In 1798, Edward Jenner introduced a much safer method of intentional infection with the cowpox virus, (smallpox vaccine), which causes a mild infection that also triggers immunity against smallpox. In 1800 the procedure was called vaccination. To avoid confusion, inoculation of smallpox is increasingly referred to as variolation, and it becomes common practice to use this term regardless of chronology. The general success and acceptance of Jenner's procedures would have led to the general nature of vaccinations developed by Pasteur and others by the end of the nineteenth century. In 1891, Pasteur expanded the definition of vaccine in honor of Jenner and subsequently became essential to qualify the term, with reference to the polio vaccine, measles vaccine, etc.
Passive
Passive immunity is the active immune transfer, in the form of readymade antibodies, from one individual to another. Passive immunity can occur naturally, when maternal antibodies are transferred to the fetus via the placenta, and can also be artificially induced, when high levels of human antibodies (or horses) specific to pathogens or toxins are transferred to non-immune individuals. Passive immunization is used when there is a high risk of infection and not enough time for the body to develop its own immune response, or to reduce ongoing or immunosuppressive illness symptoms. Passive immunity provides immediate protection, but the body does not develop memory, therefore the patient is at risk of being infected by the same pathogen in the future.
Retrieved naturally
Passive immunity of the mother is a naturally occurring type of passive immunity, and refers to immune mediated antibodies brought to the fetus by her mother during pregnancy. Maternal antibodies (MatAb) are passed through the placenta to the fetus by FcRn receptors on placental cells. This happens around the third month of pregnancy. IgG is the only isotype antibody that can cross the placenta. Passive immunity is also given by transfer of IgA antibodies found in breast milk that are transferred to the baby's intestine, protecting against bacterial infection, until newborns can synthesize antibodies. Colostrum present in the mother's milk is an example of active immunity.
Created artificially
Artificially gained passive immunity is a short-term immunization caused by antibody transfer, which can be administered in some form; as human or animal blood plasma, as a combination of human immunoglobulins for intravenous (IVIG) or intramuscular (IG) use, and in the form of monoclonal antibodies (MAb). Passive transfer is used prophylactically in cases of immunodeficiency disease, such as hypogammaglobulinemia. It is also used in the treatment of some types of acute infections, and to treat poisoning. Immunities from passive immunization last for only a short time, and there is also a potential risk for hypersensitivity reactions, and serum sickness, especially of non-human origin gamma globulins.
The induction of passive artificial immunity has been used for more than a century to treat infectious diseases, and before the advent of antibiotics, it is often the only treatment specific to certain infections. Immunoglobulin therapy continued to be the first-line therapy in the treatment of severe respiratory diseases until the 1930s, even after many sulphonamide antibiotics were introduced.
Transfer activated T cells
Passive or "transfer of adoption" of cellular immunity, given by "sensitive" transfer or T-cell activation from one individual to another. It is rarely used in humans because it requires histocompatibly compatible donors, which are often hard to find. In an unparalleled donor, this type of transfer carries a large graft risk versus host disease. It has, however, been used to treat certain diseases including some types of cancer and immunodeficiency. This type of transfer differs from bone marrow transplantation, in which hematopoietic (undifferentiated) stem cells are transferred.
Active
When B cells and T cells are activated by pathogens, memory of B-cells and T-cells develops, and the result of a primary immune response. Throughout the lifetime of animals, these memory cells will "remember" each specific pathogen encountered, and can instill a strong secondary response if the pathogen is detected again. The primary and secondary responses were first described in 1921 by the English immunologist Alexander Glenny although the mechanism involved was not discovered until later. This type of immunity is active and adaptive because the immune system prepares itself for future challenges. Active immunity often involves aspects of cellular and humoral immunity as well as input from the innate immune system.
Obtained naturally
Active immunity obtained naturally occurs when a person is exposed to a living pathogen and develops a primary immune response, leading to immunological memory. This type of immunity is "natural" because deliberate exposure does not cause it. Many impaired immune system functions can affect the formation of active immunity such as immunodeficiency (both acquired and innate forms) and immunosuppression.
Artificially obtained
Active immunity obtained artificially can be induced by vaccines, substances containing antigens. The vaccine stimulates the main response to the antigen without causing any symptoms of the disease. Richard Dunning coined the term vaccination, colleague Edward Jenner, and was adapted by Louis Pasteur for his pioneering work on vaccinations. The method Pasteur uses requires treatment of infectious agents for the disease, so they lose the ability to cause serious illness. Pasteur adopted the name of the vaccine as a general term in honor of Jenner's discovery, built by Pasteur.
In 1807, Bavaria became the first group to require the military to recruit them vaccinated against smallpox, as the spread of smallpox was associated with combat. Furthermore, the practice of vaccination will increase with widespread war.
There are four types of traditional vaccines:
- The inactivated vaccine consists of micro-organisms that have been killed with chemicals and/or heat and are no longer infectious. Examples are vaccines against flu, cholera, plague, and hepatitis A. Most vaccines of this type tend to require booster injections.
- Live, attenuated vaccines consist of micro-organisms that have been cultivated under conditions that disable their ability to induce disease. This response is more durable and generally does not require amplifier shooting. Examples include yellow fever, measles, rubella, and mumps.
- Toksoids are inactive, toxic compounds of micro-organisms in cases where these (not micro-organisms themselves) cause disease, used before encounters with toxins from micro-organisms. Examples of toxoid-based vaccines include tetanus and diphtheria.
- The subunit vaccine consists of small fragments of disease-causing organisms. A typical example is a subunit vaccine against Hepatitis B. virus
Most vaccines are given by hypodermic or intramuscular injection because they are not absorbed reliably through the intestine. Polio lives are attenuated and some typhoid and cholera vaccines are administered orally to produce immunity based on the gut.
See also
- Antiserum
- Antivenin
- Heterosubtypic immunity
- The Hoskins Effect
- Immunology
- Inoculation
- Premunitas
- An innocent vaccine
References
External links
- Immunodefinance Modeling Module of Enteric Pathogens (MIEP)
Source of the article : Wikipedia
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