allergy: …effects are the result of antibody-antigen responses (i.e., they are the products of B-cell stimulation). These can be divided into three basic types.

Baruj Benacerraf: …development of the concept of immune response (Ir) genes, which control the immune system’s ability to respond to antigens (infectious agents or foreign materials that enter the body). More than 30 Ir genes were subsequently found, and that genetic material was determined to be part of the major histocompatibility complex,…

antiserum, blood serum that contains specific antibodies against an antigen (foreign agent), such as an infective organism or poisonous substance. Antibodies in antiserum work by detecting and subsequently neutralizing antigens. Antiserums are produced in animals, most commonly horses, sheep, oxen,

therapeutics: Immunoglobulins: Immune serum globulin (ISG), obtained from the plasma of a pool of healthy donors, contains a mixture of immunoglobulins, mainly IgG, with lesser amounts of IgM and IgA. It is used to provide passive immunity to a variety of diseases such as measles, hepatitis A,…

cancer: Immune surveillance: …small tumors is known as immune surveillance.

immune system, the complex group of defense responses found in humans and other advanced vertebrates that helps repel disease-causing organisms (pathogens). Immunity from disease is actually conferred by two cooperative defense systems, called nonspecific, innate immunity and specific, acquired

immune system disorder, any of various failures in the body’s defense mechanisms against infectious organisms. Disorders of immunity include immune deficiency diseases, such as AIDS, that arise because of a diminution of some aspect of the immune response. Other types of immune disorders, such as

immune system disorder: Type III hypersensitivity: Type III, or immune-complex, reactions are characterized by tissue damage caused by the activation of complement in response to antigen-antibody (immune) complexes that are deposited in tissues. The classes of antibody involved are the same ones that participate in type II reactions—IgG…

immunity, in law, exemption or freedom from liability. In England and the United States legislators are immune from civil liability for statements made during legislative debate. They are also immune from criminal arrest, although they are subject to legal action for crime. French law and practice

immune system: Immunity from disease is actually conferred by two cooperative defense systems, called nonspecific, innate immunity and specific, acquired immunity. Nonspecific protective mechanisms repel all microorganisms equally, while the specific immune responses are tailored to particular types of invaders. Both systems work together to thwart organisms…

immunization, process by which resistance to disease is acquired or induced in plants and animals. This discussion focuses on immunization against infectious diseases specifically in humans. Active immunization via the administration of vaccines is one of the most cost-effective public health

biochemistry: Blood: …their interrelationship is known as immunochemistry.

blood: Lymphocytes: …to foreign substances is called immunologic competence (immunocompetence). Immunologic competence, which begins to develop during embryonic life, is incomplete at the time of birth but is fully established soon after birth. If an antigen is introduced into a person’s body before immunologic competence has been established, an immune response will…

biochemistry: Blood: …their interrelationship is known as immunochemistry.

immunodeficiency, defect in immunity that impairs the body’s ability to resist infection. The immune system may fail to function for many reasons. Primary immunodeficiency disorders—many of which are inherited, being caused by a genetic defect—are usually evident early in life. Secondary

antigen: …the antigen directly—is called an immunogen.

human genetics: Immunogenetics: Immunity is the ability of an individual to recognize the “self” molecules that make up one’s own body and to distinguish them from such “nonself” molecules as those found in infectious microorganisms and toxins. This process has a prominent genetic component. Knowledge of the…

antibody, a protective protein produced by the immune system in response to the presence of a foreign substance, called an antigen. Antibodies recognize and latch onto antigens in order to remove them from the body. A wide range of substances are regarded by the body as antigens, including

blood transfusion: Transfusion-induced immune reactions: These patients, described as IgA-deficient because they do not make IgA, can have a severe allergic reaction characterized by anaphylaxis with vascular collapse, severe drop in blood pressure, and respiratory distress. This problem can be treated by using washed red cells to remove the remaining plasma containing IgA or…

antibody: Antibody structure and classes: IgA, IgD, and IgE. The classes of antibody differ not only in their constant region but also in activity. For example, IgG, the most common antibody, is present mostly in the blood and tissue fluids, while IgA is found in the mucous membranes lining the respiratory and gastrointestinal…

mesothelioma: Diagnosis and subtypes of mesothelioma: …requires that a battery of immunohistochemistry (IHC) tests be performed on each tumour to determine whether it is mesothelioma or perhaps another type of tumour that has spread to the thoracic or abdominal cavity. IHC uses colorimetric antibodies directed at proteins on the surfaces of cells. A pattern of both…

immunologic blood test, any of a group of diagnostic analyses of blood that employ antigens (foreign proteins) and antibodies (immunoglobulins) to detect abnormalities of the immune system. Immunity to disease depends on the body’s ability to produce antibodies when challenged by antigens.

blood: Lymphocytes: …to foreign substances is called immunologic competence (immunocompetence). Immunologic competence, which begins to develop during embryonic life, is incomplete at the time of birth but is fully established soon after birth. If an antigen is introduced into a person’s body before immunologic competence has been established, an immune response will…

human disease: Autoimmune disorders: …state is referred to as immunologic ignorance. Autoimmune diseases arise when this mechanism fails and self-reactive lymphocytes are activated by self-antigens in the host’s own tissues, often with devastating effects. Systemic lupus erythematosus, thyroiditis, insulin-dependent diabetes mellitus, and rheumatoid arthritis are examples of this type of disorder.

lymphocyte: Types and functions of lymphocytes: These cells account for immunologic “memory,” a more rapid, vigorous response to a second encounter with the same antigen.

allergy: …effects are the result of antibody-antigen responses (i.e., they are the products of B-cell stimulation). These can be divided into three basic types.

immune system, the complex group of defense responses found in humans and other advanced vertebrates that helps repel disease-causing organisms (pathogens). Immunity from disease is actually conferred by two cooperative defense systems, called nonspecific, innate immunity and specific, acquired

immunology, the scientific study of the body’s resistance to invasion by other organisms (i.e., immunity). In a medical sense, immunology deals with the body’s system of defense against disease-causing microorganisms and with disorders in that system’s functioning. The artificial induction of

rapamycin: It acts specifically on FK-binding protein 12 (FKBP12), a substance commonly referred to as an immunophilin because it binds to immunosuppressive drugs. In turn, the rapamycin-FKBP12 complex binds to the mammalian target of rapamycin (mTOR), a kinase (an enzyme that adds phosphate groups to other molecules) that plays a…

plant disease: Technological advances in the identification of pathogenic agents: …microscopy have been applied to immunosorbent electron microscopy, in which the specimen is subject to an antigen-antibody reaction before observation and scanning tunneling microscopy, which provides information about the surface of a specimen by constructing a three-dimensional image.

immunosuppressant, any agent in a class of drugs that is capable of inhibiting the immune system. Immunosuppressants are used primarily to prevent the rejection of an organ following transplantation and in the treatment of autoimmune disease disease. Among the agents that are most effective for

immunosuppression, reduction in the ability of the immune system to defend against disease or infection. Immunosuppression may be induced by certain diseases, such AIDS, lupus erythematosus, rheumatoid arthritis, or type 1 diabetes mellitus. Additionally, suppression of immunity often occurs as a

immunosuppressant, any agent in a class of drugs that is capable of inhibiting the immune system. Immunosuppressants are used primarily to prevent the rejection of an organ following transplantation and in the treatment of autoimmune disease disease. Among the agents that are most effective for

immunotherapy, medical treatment in which the body’s own cells or chemicals are used to help the natural immune response work against disease. Immunotherapy is mainly used in the treatment of cancer, though it is also sometimes used to treat autoimmune diseases. Immunotherapy leverages the ability

Imo, state, southern Nigeria. Imo is bordered by the states of Anambra to the north, Abia (until 1991 part of Imo state) to the east, and Rivers to the south and west. The British first entered the territory in 1901, when they established a military post in the region. Imo consists of coastal

weather forecasting: Establishment of weather-station networks and services: …1880 they had formed the International Meteorological Organization (IMO).

International Maritime Organization (IMO), United Nations (UN) specialized agency created to develop international treaties and other mechanisms on maritime safety; to discourage discriminatory and restrictive practices in international trade and unfair practices by shipping concerns; and to reduce

antidiarrheal drug: such as codeine and loperamide (Imodium), and anticholinergic drugs, such as dicyclomine and atropine, may be used to slow intestinal motility and to relieve pain associated with abdominal cramping. The opiate derivative diphenoxylate typically is given with atropine in a combination marketed as Lomotil. Although opioids carry a risk…

Cymbeline: …Britain, decides that his daughter, Imogen, must marry his horrid stepson Cloten. When Cymbeline learns that Imogen is secretly married to Posthumus, he banishes Posthumus, who heads for Rome. In a conversation with a villainous Italian, Iachimo, Posthumus finds himself drawn unwisely into betting Iachimo that Imogen’s fidelity to her…

clay mineral: Imogolite and allophane: Imogolite is an aluminosilicate with an approximate composition of SiO2 · Al2O3 · 2.5H2O. This mineral was discovered in 1962 in a soil derived from glassy volcanic ash known as “imogo.” Electron-optical observations indicate that imogolite has a unique morphological feature of…

Imola, town and episcopal see, Emilia-Romagna regione, northern Italy. Imola lies along the Santerno River, southeast of Bologna. Its Forum Cornelii was a station on the Roman road Via Aemilia. The town was devastated in the 6th century by the Byzantine emperor Justinian I but was rebuilt and

rimu, (Dacrydium cupressinum), coniferous timber tree of the family Podocarpaceae, native to New Zealand. The rimu tree may attain a height of 45 metres (150 feet) or more. The wood is reddish brown to yellowish brown, with a distinctive figuring, or marking, of light and dark streaks. It is made

Imhotep was a vizier, sage, architect, astrologer, and chief minister to Djoser (reigned c. 2592–c. 2566 bce), the first king of Egypt’s third dynasty, who was later worshipped as the god of medicine in Egypt and in Greece, where he was identified with the Greek god of medicine, Asclepius. He is

Robert Kahn: …group that designed the network’s Interface Message Processor, which would mediate between the network and each institution’s host computer. Second, and perhaps more important, in 1972 Kahn helped organize the first International Conference on Computer Communication, which served as the ARPANET’s public debut.

collision, in physics, the sudden, forceful coming together in direct contact of two bodies, such as, for example, two billiard balls, a golf club and a ball, a hammer and a nail head, two railroad cars when being coupled together, or a falling object and a floor. Apart from the properties of the

meteorite crater: The impact-cratering process: Craters with megaterraces are called impact basins.

meteorite crater, depression that results from the impact of a natural object from interplanetary space with Earth or with other comparatively large solid bodies such as the Moon, other planets and their satellites, or larger asteroids and comets. For this discussion, the term meteorite crater is

impact event, collision of astronomical objects. Most collisions involve asteroids, comets, or meteoroids colliding with larger objects, such as planets or moons. Most impact events involve relatively small objects, but others involve large objects ranging from 100 metres (300 feet) to many

forging: Impact forging is essentially hammer forging in which both dies are moved horizontally, converging on the workpiece. Counterblow forging is similar, except that the dies converge vertically. A principal advantage of these last two methods is that the two dies mutually absorb energy, eliminating the…

bomb: Guidance and arming: Impact fuzes, historically the most common type, are set in the bomb’s nose and detonate upon impact, setting off the main charge. A time fuze, by contrast, acts after a controlled delay. Another type, the proximity fuze, senses when a target is close enough to…

bomb: Guidance and arming: Impact fuzes, historically the most common type, are set in the bomb’s nose and detonate upon impact, setting off the main charge. A time fuze, by contrast, acts after a controlled delay. Another type, the proximity fuze, senses when a target is close enough to…

impact injury, the damage caused by the collision of a body with a moving or stationary object. Impact injuries can occur in any accident involving moving vehicles, such as automobiles, motorcycles, and trains, parachute landings, seat ejections, aircraft crashes, rocket accelerations and

mass spectrometry: Electron bombardment: Electron impact has remained the most widely used method of ionization in mass spectrometry. It is subject to problems common to the arc: an almost total lack of selectivity as to the chemical element ionized and, to a lesser extent, the production of ions with degrees…

collective behavior: Impact and stocktaking period: In disasters such as floods and some hurricanes there is a distinctly long period of impact, which can be separated from a subsequent period of stocktaking or immobility. In earthquakes and explosions, on the other hand, the impact is so brief…

information processing: Printers: …they produce images on paper: impact and nonimpact. In the first type, images are formed by the print mechanism making contact with the paper through an ink-coated ribbon. The mechanism consists either of print hammers shaped like characters or of a print head containing a row of pins that produce…

impact structure, remains of an ancient meteorite impact on Earth’s surface, generally in the form of a circular scar of crushed and deformed bedrock. Because such telltale features as crater walls, fused silica glass, and meteorite fragments are heavily modified over time by erosion and

impact test, Test of the ability of a material to withstand impact, used by engineers to predict its behaviour under actual conditions. Many materials fail suddenly under impact, at flaws, cracks, or notches. The most common impact tests use a swinging pendulum to strike a notched bar; heights

Earth impact hazard: …depression of surface temperatures—a so-called impact winter—leading to loss of photosynthesizing plant life and worldwide starvation and disease.

wrench: Power or impact wrenches are used for tightening or loosening nuts quickly. They are essentially small handheld electric or pneumatic motors that can rotate socket wrenches at high speed. They are equipped with a torque-limiting device that will stop the rotation of the socket wrench when a…

fracture: An impacted fracture occurs when the broken ends of the bone are jammed together by the force of the injury. A comminuted fracture is one in which the broken ends of the bone are shattered into many pieces. Fractures can also be classified by their configuration…

deafness, partial or total inability to hear. The two principal types of deafness are conduction deafness and nerve deafness. In conduction deafness, there is interruption of the sound vibrations in their passage from the outer world to the nerve cells in the inner ear. The obstacle may be earwax

fatigue: …be lumped under the term impairment, mentioned originally as one of the major forms of human inadequacy. While transient impairment and personalistic fatigue generally have not been distinguished from each other by many psychologists, in numerous studies impairment, rather than the feeling of fatigue, has been the point of interest.

impala, (Aepyceros melampus), swift-running antelope, the most abundant ruminant in the savannas of eastern and southern Africa. It is often seen in large breeding herds closely shepherded by a territorial male. The impala can be described as perfection in an antelope; it is both beautiful and

Apocynaceae: Major genera and species: The impala lily (Adenium multiflorum) is an ornamental shrub with star-shaped flowers and large underground tubers.

heraldry: Other charges: Impalement means the division of the shield into two equal parts by a straight line from the top to bottom. That method is used to show either the arms of husband and wife, the arms of the husband being in the dexter half, or certain…

Llewelyn Powys: …he suffered until his death); Impassioned Clay (1931), an exploration of spirituality; and Love and Death (1939), a partly fictionalized account of and reflection on a love affair.

impasto, paint that is applied to a canvas or panel in quantities that make it stand out from the surface. Impasto was used frequently to mimic the broken-textured quality of highlights—i.e., the surfaces of objects that are struck by an intense light. Impasto came into its own in the 17th century,

Impatiens, large genus of herbaceous plants belonging to the family Balsaminaceae. Impatiens are widely distributed in Asia, Africa, and North America, and several are popular garden plants. Impatiens bear simple leaves that are usually alternately arranged along the stem. The upper leaves are

Impatiens: The garden balsam (Impatiens balsamina) is native to the tropics of Asia but has long been cultivated in temperate regions of the world. The plant is an annual that grows about 75 cm (30 inches) in height and has many horticultural forms with flowers of almost…

Impatiens: Spotted jewelweed (I. capensis) and pale touch-me-not (or pale snapweed, I. pallida) are common weeds native to extensive regions of eastern North America. Spotted jewelweed grows up to 150 cm (59 inches) tall and bears orange flowers spotted with red or brown, while pale touch-me-not…

Impatiens: The western touch-me-not (I. noli-tangere) is native to western North America, Europe, and Asia.

Impatiens: capensis) and pale touch-me-not (or pale snapweed, I. pallida) are common weeds native to extensive regions of eastern North America. Spotted jewelweed grows up to 150 cm (59 inches) tall and bears orange flowers spotted with red or brown, while pale touch-me-not has larger, yellower flowers. The…

Assia Djebar: It was followed by Les Impatients (1958; “The Impatient Ones”), which similarly dealt with young women within the colonial Algerian bourgeois milieu.

impeachment, in common law, a proceeding instituted by a legislative body to address serious misconduct by a public official. In Great Britain the House of Commons serves as prosecutor and the House of Lords as judge in an impeachment proceeding. In the federal government of the United States, the

The U.S. Constitution gives the House of Representatives the sole power to formally charge a federal official who is suspected of committing a crime or abuse of power, using a process called impeachment. If the House approves the articles of impeachment (the charges of wrongdoing) in a majority

In the wake of the Watergate scandal and the resignation of U.S. Pres. Richard M. Nixon, Bruce L. Felknor, a former executive director of the Fair Campaign Practices Committee and the author of Dirty Politics (1966), contributed a Special Report to the 1975 Britannica Book of the Year on the role

Edie Falco: …Hillary Clinton in the miniseries Impeachment: American Crime Story (2021), which focuses on the impeachment of Pres. Bill Clinton.

human ear: Audiometry: …and brainstem is supplied by impedance audiometry. Two small tubes are sealed into the external canal. Through one tube sound from a small loudspeaker is injected into the canal. The portion that is reflected from the tympanic membrane is picked up by the other tube and led to a microphone,…

sound: Impedance mismatch: Mediums in which the speed of sound is different generally have differing acoustic impedances, so that, when a sound wave strikes an interface between the two, it encounters an impedance mismatch. As a result, some of the wave reflects while some is transmitted…

transformer: Impedance-matching transformers are used to match the impedance of a source and that of its load, for most efficient transfer of energy. Isolation transformers are usually employed for reasons of safety to isolate a piece of equipment from the source of power.

Protestantism: Pietism in the 17th century: While in Dresden he wrote Impediments to Theological Study (1690), which was hardly calculated to win friends at the famous University of Leipzig, and made the acquaintance of a young instructor, August Hermann Francke (1663–1727), who became his successor and the second great leader of Pietism.

centrifugal pump: …of the device are the impeller (a wheel with vanes) and the circular pump casing around it. In the most common type, called the volute centrifugal pump, fluid enters the pump at high speed near the centre of the rotating impeller and is thrown against the casing by the vanes.…

Hinton Rowan Helper: …1857 with the publication of The Impending Crisis of the South: How to Meet It, in which he attacked slavery not because it exploited the black bondsman but because it victimized nonslaveholding whites and inhibited Southern economic progress. As almost the only Southern protest against slavery since early in the…

cogon grass, (Imperata cylindrica), species of perennial grass in the family Poaceae, native to temperate and tropical regions of the Old World. Cogon grass is a serious weed in cultivated areas of South Africa and Australia and is considered an invasive species in many areas outside its native

Indo-European languages: Verbal inflection: Verbs with imperative endings belonged to the imperative mood (used for commands)—e.g., *H1s-dhí ‘be (singular),’ *H1és-tu ‘let him be.’ Verbs with primary endings were marked as non-past (present or future) in tense and indicative in mood—e.g., *H1és-ti ‘he is.’ (Indicative mood signifies objective statements and questions.) Verbs…

computer science: Programming languages: …for example) are known as imperative languages, since they specify as a sequence of explicit commands how the machine is to go about solving the problem at hand. These languages were also known as procedural languages, since they allowed programmers to develop and reuse procedures, subroutines, and functions to avoid…

mood: …three moods: the indicative, the imperative, and the subjunctive. The indicative is generally used for factual or neutral situations, as in English “John did his work” and Spanish “Juan hizo su trabajo.” The imperative conveys commands or requests—for example, “Do your work.” It is distinguished by the absence of an…

emperor, title designating the sovereign of an empire, conferred originally on rulers of the ancient Roman Empire and on various later European rulers, though the term is also applied descriptively to some non-European monarchs. In republican Rome (c. 509–27 bce), imperator denoted a victorious

Suzan-Lori Parks: …Awards for her third play, Imperceptible Mutabilities in the Third Kingdom (produced 1989), and for her eighth, Venus (produced 1996), about a South African Khoisan woman taken to England as a sideshow attraction. With Topdog/Underdog (produced 2001), Parks evoked the complexities of the African American experience through the fraught relationship…

universal: Problems for resemblance nominalism: …“companionship problem” and the “imperfect community” problem. If two distinct properties always happen to be companions—e.g., if all and only red things happen to be round—the method of constructing natural classes would incorrectly determine only one class for what intuitively seems to be two properties, or two respects in…

market: Modifications of the theory: A theory of imperfect competition was invented to reconcile the traditional theory with under-capacity working but was attacked as unrealistic. The upshot was a general recognition that strict profit maximizing is impossible in conditions of uncertainty; that prices of manufactures are generally formed by adding a margin to…

angiosperm: General features: …carpels, and a unisexual (or “imperfect”) flower either lacks stamens (and is called carpellate) or lacks carpels (and is called staminate). Species with both staminate flowers and carpellate flowers on the same plant (e.g., corn) are monoecious, from the Greek for “one house.” Species in which the staminate flowers are…

game theory: Games of imperfect information: A “saddlepoint” in a two-person constant-sum game is the outcome that rational players would choose. (Its name derives from its being the minimum of a row that is also the maximum of a column in a payoff matrix—to be illustrated shortly—which corresponds to…

Lewis Allen: In 1947 Allen directed The Imperfect Lady, a period drama about a politician (Ray Milland) who falls for a music-hall dancer (Teresa Wright) in 1890s London, and the crime yarn Desert Fury, in which a police officer (Burt Lancaster) wrests his former girlfriend (Lizabeth Scott) away from a compulsive

Anne Roiphe: Other notable fictional works include An Imperfect Lens (2006), which follows three scientists who travel to Alexandria, Egypt, during a cholera epidemic in 1883, and Ballad of the Black and Blue Mind (2015), about a psychoanalyst and her patients.

Indo-European languages: Verbal inflection: The imperfective aspect, traditionally called “present,” was used for repeated actions and for ongoing processes or states—e.g., *stí-stH2-(e)- ‘stand up more than once, be in the process of standing up,’ *mn̥-yé- ‘ponder, think,’ *H1es- ‘be.’ The perfective aspect, traditionally called “aorist,” expressed a single, completed occurrence…

Imperia, town, Liguria regione, northwestern Italy. It lies on that part of the Riviera di Ponente known as the Riviera dei Fiori, northeast of San Remo. Formed in 1923 by the union of Porto Maurizio, Oneglia, and several villages, the town took its name from the Torrente Impero (“Impero Stream”)

Araucanía: Two partially navigable rivers, the Imperial and the Toltén, traverse the southern Araucanía region from east to west. The cordilleran ridges and volcanoes at Tolguaca, Lonquimay, and Llaima and the forests, lakes, and hot springs at Tolguaca, Río Blanco, and Manzanares are prime scenic attractions. Tourism, however, ranks below farming…

Brazil: Visual arts: …of Emperor Pedro II, the Imperial Academy of Fine Arts in Rio de Janeiro drove the development of Brazilian painting, which was largely influenced by Neoclassical and Romantic styles. The academy organized art collections, held exhibitions and competitions, and trained a number of Brazilian artists who specialized in the painting…

British Airways PLC: ) merged to form Imperial Airways Ltd., one of the pioneers of intercontinental air routes. Inheriting 1,760 miles (2,830 km) of British and cross-Channel routes, Imperial Airways spanned Europe and Asia as far as India, Malaya, Hong Kong, and Australia and linked imperial territories in Africa as far as…