Biofelsefe — İmmünoloji
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📹 Immunology in the skin / Nature video (VİDEO)

📹 Immunology in the skin / Nature video (LINK)

The skin is the body's main barrier against physical insults and microbial pathogens. Diverse and functionally specialized subsets of immune cells in the skin sense and respond to infection or various barrier breaches to activate an immune response and eventually, return to homeostasis. However, deregulated immune responses can also cause skin disorders, such as psoriasis.


📹 Immunology in the Gut Mucosa / Nature video (VİDEO)

📹 Immunology in the Gut Mucosa / Nature video (LINK)

The gut mucosa hosts the body's largest population of immune cells. Nature Immunology in collaboration with Arkitek Studios have produced an animation unravelling the complexities of mucosal immunology in health and disease.



  Immunology (W)


Immunology (W)

Title: MRSA, Ingestion by Neutrophil Description: MRSA (yellow) being ingested by neutrophil (purple). Categories: Research in NIH Labs and Clinics Type: Color, Photo Source: National Institute of Allergy and Infectious Diseases (NIAID) Date Created: 2009.

Immunology is a branch of biology that covers the study of immune systems in all organisms. Immunology charts, measures, and contextualizes the physiological functioning of the immune system in states of both health and diseases; malfunctions of the immune system in immunological disorders (such as autoimmune diseases, hypersensitivities, immune deficiency, and transplant rejection); and the physical, chemical, and physiological characteristics of the components of the immune system in vitro, in situ, and in vivo.

Immunology has applications in numerous disciplines of medicine, particularly in the fields of organ transplantation, oncology, rheumatology, virology, bacteriology, parasitology, psychiatry, and dermatology.

The term was coined by Russian biologist Ilya Ilyich Mechnikov, who advanced studies on immunology and received the Nobel Prize for his work in 1908. He pinned small thorns into starfish larvae and noticed unusual cells surrounding the thorns. This was the active response of the body trying to maintain its integrity. It was Mechnikov who first observed the phenomenon of phagocytosis, in which the body defends itself against a foreign body.

Prior to the designation of immunity, from the etymological root immunis, which is Latin for “exempt,” early physicians characterized organs that would later be proven as essential components of the immune system. The important lymphoid organs of the immune system are the thymus, bone marrow, and chief lymphatic tissues such as spleen, tonsils, lymph vessels, lymph nodes, adenoids, and liver. When health conditions worsen to emergency status, portions of immune system organs, including the thymus, spleen, bone marrow, lymph nodes, and other lymphatic tissues, can be surgically excised for examination while patients are still alive.

Many components of the immune system are typically cellular in nature and not associated with any specific organ, but rather are embedded or circulating in various tissues located throughout the body.

Classical immunology

Classical immunology

Classical immunology (W)

Classical immunology ties in with the fields of epidemiology and medicine. It studies the relationship between the body systems, pathogens, and immunity. The earliest written mention of immunity can be traced back to the plague of Athens in 430 BCE. 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. Many other ancient societies have references to this phenomenon, but it was not until the 19th and 20th centuries before the concept developed into scientific theory.

The study of the molecular and cellular components that comprise the immune system, including their function and interaction, is the central science of immunology. The immune system has been divided into a more primitive innate immune system and, in vertebrates, an acquired or adaptive immune system. The latter is further divided into humoral (or antibody) and cell-mediated components.

The immune system has the capability of self and non-self-recognition. An antigen is a substance that ignites the immune response. The cells involved in recognizing the antigen are Lymphocytes. Once they recognize, they secrete antibodies. Antibodies are proteins that neutralize the disease-causing microorganisms. Antibodies don't directly kill pathogens, but instead, identify antigens as targets for destruction by other immune cells such as phagocytes or NK cells.

The humoral (antibody) response is defined as the interaction between antibodies and antigens. Antibodies are specific proteins released from a certain class of immune cells known as B lymphocytes, while antigens are defined as anything that elicits the generation of antibodies ("anti"body "gen"erators). Immunology rests on an understanding of the properties of these two biological entities and the cellular response to both.

It's now getting clear that the immune responses contribute to the development of many common disorders not traditionally viewed as immunologic, including metabolic, cardiovascular, cancer, and neurodegenerative conditions like Alzheimer’s disease. Besides, there are direct implications of the immune system in the infectious diseases (tuberculosis, malaria, hepatitis, pneumonia, dysentery, and helminth infestations) as well. Hence, research in the field of immunology is of prime importance for the advancements in the fields of modern medicine, biomedical research, and biotechnology.

Immunological research continues to become more specialized, pursuing non-classical models of immunity and functions of cells, organs and systems not previously associated with the immune system (Yemeserach 2010).


Clinical immunology

Clinical immunology

Clinical immunology (W)

Clinical immunology is the study of diseases caused by disorders of the immune system (failure, aberrant action, and malignant growth of the cellular elements of the system). It also involves diseases of other systems, where immune reactions play a part in the pathology and clinical features.

The diseases caused by disorders of the immune system fall into two broad categories:

Other immune system disorders include various hypersensitivities (such as in asthma and other allergies) that respond inappropriately to otherwise harmless compounds.

The most well-known disease that affects the immune system itself is AIDS, an immunodeficiency characterized by the suppression of CD4+ ("helper") T cells, dendritic cells and macrophages by the Human Immunodeficiency Virus (HIV).

Clinical immunologists also study ways to prevent the immune system's attempts to destroy allografts (transplant rejection).


Developmental immunology

Developmental immunology

Developmental immunology (W)

The body’s capability to react to antigens depends on a person's age, antigen type, maternal factors and the area where the antigen is presented. Neonates are said to be in a state of physiological immunodeficiency, because both their innate and adaptive immunological responses are greatly suppressed. Once born, a child’s immune system responds favorably to protein antigens while not as well to glycoproteins and polysaccharides. In fact, many of the infections acquired by neonates are caused by low virulence organisms like Staphylococcus and Pseudomonas. In neonates, opsonic activity and the ability to activate the complement cascade is very limited. For example, the mean level of C3 in a newborn is approximately 65% of that found in the adult. Phagocytic activity is also greatly impaired in newborns. This is due to lower opsonic activity, as well as diminished up-regulation of integrin and selectin receptors, which limit the ability of neutrophils to interact with adhesion molecules in the endothelium. Their monocytes are slow and have a reduced ATP production, which also limits the newborn's phagocytic activity. Although, the number of total lymphocytes is significantly higher than in adults, the cellular and humoral immunity is also impaired. Antigen-presenting cells in newborns have a reduced capability to activate T cells. Also, T cells of a newborn proliferate poorly and produce very small amounts of cytokines like IL-2, IL-4, IL-5, IL-12, and IFN-g which limits their capacity to activate the humoral response as well as the phagocitic activity of macrophage. B cells develop early during gestation but are not fully active.

Maternal factors also play a role in the body’s immune response. At birth, most of the immunoglobulin present is maternal IgG. Because IgM, IgD, IgE and IgA don't cross the placenta, they are almost undetectable at birth. Some IgA is provided by breast milk. These passively-acquired antibodies can protect the newborn for up to 18 months, but their response is usually short-lived and of low affinity. These antibodies can also produce a negative response. If a child is exposed to the antibody for a particular antigen before being exposed to the antigen itself then the child will produce a dampened response. Passively acquired maternal antibodies can suppress the antibody response to active immunization. Similarly, the response of T-cells to vaccination differs in children compared to adults, and vaccines that induce Th1 responses in adults do not readily elicit these same responses in neonates. Between six and nine months after birth, a child’s immune system begins to respond more strongly to glycoproteins, but there is usually no marked improvement in their response to polysaccharides until they are at least one year old. This can be the reason for distinct time frames found in vaccination schedules.

During adolescence, the human body undergoes various physical, physiological and immunological changes triggered and mediated by hormones, of which the most significant in females is 17-β-estradiol (an estrogen) and, in males, is testosterone. Estradiol usually begins to act around the age of 10 and testosterone some months later. There is evidence that these steroids not only act directly on the primary and secondary sexual characteristics but also have an effect on the development and regulation of the immune system, including an increased risk in developing pubescent and post-pubescent autoimmunity. There is also some evidence that cell surface receptors on B cells and macrophages may detect sex hormones in the system.

The female sex hormone 17-β-estradiol has been shown to regulate the level of immunological response, while some male androgens such as testosterone seem to suppress the stress response to infection. Other androgens, however, such as DHEA, increase immune response. As in females, the male sex hormones seem to have more control of the immune system during puberty and post-puberty than during the rest of a male's adult life.

Physical changes during puberty such as thymic involution also affect immunological response.


Ecoimmunology and behavioural immunity

Ecoimmunology and behavioural immunity

Ecoimmunology and behavioural immunity (W)

Ecoimmunology, or ecological immunology, explores the relationship between the immune system of an organism and its social, biotic and abiotic environment.

More recent ecoimmunological research has focused on host pathogen defences traditionally considered "non-immunological", such as pathogen avoidance, self-medication, symbiont-mediated defenses, and fecundity trade-offs. Behavioural immunity, a phrase coined by Mark Schaller, specifically refers to psychological pathogen avoidance drivers, such as disgust aroused by stimuli encountered around pathogen-infected individuals, such as the smell of vomit. More broadly, "behavioural" ecological immunity has been demonstrated in multiple species. For example, the Monarch butterfly often lays its eggs on certain toxic milkweed species when infected with parasites. These toxins reduce parasite growth in the offspring of the infected Monarch. However, when uninfected Monarch butterflies are forced to feed only on these toxic plants, they suffer a fitness cost as reduced lifespan relative to other uninfected Monarch butterflies. This indicates that laying eggs on toxic plants is a costly behaviour in Monarchs which has probably evolved to reduce the severity of parasite infection.

Symbiont-mediated defenses are also heritable across host generations, despite a non-genetic direct basis for the transmission. Aphids, for example, rely on several different symbionts for defense from key parasites, and can vertically transmit their symbionts from parent to offspring. Therefore, a symbiont that successfully confers protection from a parasite is more likely to be passed to the host offspring, allowing coevolution with parasites attacking the host in a way similar to traditional immunity.




Immunotherapy (W)

Main article: Immunotherapy

The use of immune system components or antigens to treat a disease or disorder is known as immunotherapy. Immunotherapy is most commonly used to treat allergies, autoimmune disorders such as Crohn’s disease and rheumatoid arthritis, and certain cancers. Immunotherapy is also often used in the immunosuppressed (such as HIV patients) and people suffering from other immune deficiencies. This includes regulating factors such as IL-2, IL-10, GM-CSF B, IFN-α.


Diagnostic immunology

Diagnostic immunology

Diagnostic immunology (W)

Main article: Immunodiagnostics

The specificity of the bond between antibody and antigen has made the antibody an excellent tool for the detection of substances by a variety of diagnostic techniques. Antibodies specific for a desired antigen can be conjugated with an isotopic (radio) or fluorescent label or with a color-forming enzyme in order to detect it. However, the similarity between some antigens can lead to false positives and other errors in such tests by antibodies cross-reacting with antigens that aren't exact matches.


Cancer immunology

Cancer immunology

Cancer immunology (W)

Main article: Cancer immunology

The study of the interaction of the immune system with cancer cells can lead to diagnostic tests and therapies with which to find and fight cancer. The immunology concerned with physiological reaction characteristic of the immune state.


Reproductive immunology

Reproductive immunology

Reproductive immunology (W)

This area of the immunology is devoted to the study of immunological aspects of the reproductive process including fetus acceptance. The term has also been used by fertility clinics to address fertility problems, recurrent miscarriages, premature deliveries and dangerous complications such as pre-eclampsia.


Theoretical immunology

Theoretical immunology

Theoretical immunology (W)

Immunology is strongly experimental in everyday practice but is also characterized by an ongoing theoretical attitude. Many theories have been suggested in immunology from the end of the nineteenth century up to the present time. The end of the 19th century and the beginning of the 20th century saw a battle between "cellular" and "humoral" theories of immunity. According to the cellular theory of immunity, represented in particular by Elie Metchnikoff, it was cells – more precisely, phagocytes – that were responsible for immune responses. In contrast, the humoral theory of immunity, held by Robert Koch and Emil von Behring, among others, stated that the active immune agents were soluble components (molecules) found in the organism's "humors" rather than its cells.

In the mid-1950s, Macfarlane Burnet, inspired by a suggestion made by Niels Jerne, formulated the clonal selection theory (CST) of immunity. On the basis of CST, Burnet developed a theory of how an immune response is triggered according to the self/nonself distinction: "self" constituents (constituents of the body) do not trigger destructive immune responses, while "nonself" entities (e.g., pathogens, an allograft) trigger a destructive immune response. The theory was later modified to reflect new discoveries regarding histocompatibility or the complex "two-signal" activation of T cells. The self/nonself theory of immunity and the self/nonself vocabulary have been criticized, but remain very influential.

More recently, several theoretical frameworks have been suggested in immunology, including "autopoietic" views, "cognitive immune" views, the "danger model" (or "danger theory"), and the "discontinuity" theory. The danger model, suggested by Polly Matzinger and colleagues, has been very influential, arousing many comments and discussions.


See also


  Immunology (history of medicine) (B)

Immunology (history of medicine) (B)

Immunology (history of medicine) (B)

Immunology (B)

Dramatic though they undoubtedly were, the advances in chemotherapy still left one important area vulnerable, that of the viruses. It was in bringing viruses under control that advances in immunology—the study of immunity—played such a striking part. One of the paradoxes of medicine is that the first large-scale immunization against a viral disease was instituted and established long before viruses were discovered. When Edward Jenner introduced vaccination against the virus that causes smallpox, the identification of viruses was still 100 years in the future. It took almost another half century to discover an effective method of producing antiviral vaccines that were both safe and effective.

In the meantime, however, the process by which the body reacts against infectious organisms to generate immunity became better understood. In Paris, Élie Metchnikoff had already detected the role of white blood cells in the immune reaction, and Jules Bordet had identified antibodies in the blood serum. The mechanisms of antibody activity were used to devise diagnostic tests for a number of diseases. In 1906 August von Wassermann gave his name to the blood test for syphilis, and in 1908 Charles Mantoux developed a skin test for tuberculosis. At the same time, methods of producing effective substances for inoculation were improved, and immunization against bacterial diseases made rapid progress.

Antibacterial vaccination

Antibacterial vaccination

Antibacterial vaccination (B)

In 1897 English bacteriologist Almroth Wright introduced a vaccine prepared from killed typhoid bacilli as a preventive of typhoid. Preliminary trials in the Indian army produced excellent results, and typhoid vaccination was adopted for the use of British troops serving in the South African War. Unfortunately, the method of administration was inadequately controlled, and the government sanctioned inoculations only for soldiers that “voluntarily presented themselves for this purpose prior to their embarkation for the seat of war.” The result was that, according to the official records, only 14,626 men volunteered out of a total strength of 328,244 who served during the three years of the war. Although later analysis showed that inoculation had had a beneficial effect, there were 57,684 cases of typhoid—approximately one in six of the British troops engaged—with 9,022 deaths.

A bitter controversy over the merits of the vaccine followed, but immunization was officially adopted by the army before the outbreak of World War I. Comparative statistics would seem to provide striking confirmation of the value of antityphoid inoculation, even allowing for the better sanitary arrangements in the latter war. In the South African War the annual incidence of enteric infections (typhoid and paratyphoid) was 105 per 1,000 troops, and the annual death rate was 14.6 per 1,000. The comparable figures for World War I were 2.35 and 0.139, respectively.

It is perhaps a sign of the increasingly critical outlook that developed in medicine in the post-1945 era that experts continued to differ on some aspects of typhoid immunization. There was no question as to its fundamental efficacy, but there was considerable variation of opinion as to the best vaccine to use and the most effective way of administering it. Moreover, it was often difficult to decide to what extent the decline in typhoid was attributable to improved sanitary conditions and to what extent it was due to greater use of the vaccine.


The other great hazard of war that was brought under control in World War I was tetanus. This was achieved by the prophylactic injection of tetanus antitoxin into all wounded men. The serum was originally prepared by the bacteriologists Emil von Behring and Shibasaburo Kitasato in 1890–92, and the results of this first large-scale trial amply confirmed its efficacy. (Tetanus antitoxin is a sterile solution of antibody globulins—a type of blood protein—from immunized horses or cattle.)

It was not until the 1930s, however, that an efficient vaccine, or toxoid, as it is known in the cases of tetanus and diphtheria, was produced against tetanus. (Tetanus toxoid is a preparation of the toxin—or poison—produced by the microorganism. Injected into humans, it stimulates the body’s own defenses against the disease, thus bringing about immunity.) Again, a war was to provide the opportunity for testing on a large scale, and experience with tetanus toxoid in World War II indicated that it gave a high degree of protection.


The story of diphtheria is comparable to that of tetanus, though even more dramatic. First, as with tetanus antitoxin, came the preparation of diphtheria antitoxin by Behring and Kitasato in 1890. As the antitoxin came into general use for the treatment of cases, the death rate began to decline. There was no significant fall in the number of cases, however, until a toxin–antitoxin mixture, introduced by Behring in 1913, was used to immunize children. A more effective toxoid was introduced by French bacteriologist Gaston Ramon in 1923, and with subsequent improvements this became one of the most effective vaccines available in medicine. Where mass immunization of children with the toxoid was practiced, as in the United States and Canada beginning in the late 1930s and in England and Wales in the early 1940s, cases of diphtheria and deaths from the disease became almost nonexistent. In England and Wales, for instance, the number of deaths fell from an annual average of 1,830 in 1940–44 to zero in 1969.

Administration of a combined vaccine against diphtheria, pertussis (whooping cough), and tetanus (DPT) was recommended for young children. Although dangerous side effects from the DPT vaccine were initially reported, the vaccine was improved. Modern combined vaccines against diphtheria, tetanus, and pertussis are generally safe and are used in most countries because of the protection they afford.

BCG vaccine for tuberculosis

If, as is universally accepted, prevention is better than cure, immunization is the ideal way of dealing with diseases caused by microorganisms. An effective safe vaccine protects the individual from disease, whereas chemotherapy merely copes with the infection once the individual has been affected. In spite of its undoubted value, however, immunization has been a recurring source of dispute. Like vaccination against typhoid (and, later, against polio), tuberculosis immunization evoked widespread contention.

In 1908 Albert Calmette, a pupil of Pasteur, and Camille Guérin produced an avirulent (weakened) strain of the tubercle bacillus. About 13 years later, vaccination of children against tuberculosis was introduced, with a vaccine made from this avirulent strain and known as BCG (bacillus Calmette-Guérin) vaccine. Although it was adopted in France, Scandinavia, and elsewhere, British and U.S. authorities frowned upon its use on the grounds that it was not safe and that the statistical evidence in its favour was not convincing.

One of the stumbling blocks in the way of its widespread adoption was what came to be known as the Lübeck disaster. In the spring of 1930 in Lübeck, Germany, 249 infants were vaccinated with BCG vaccine, and by autumn 73 of the 249 were dead. Criminal proceedings were instituted against those responsible for giving the vaccine. The final verdict was that the vaccine had been contaminated, and the BCG vaccine itself was exonerated from any responsibility for the deaths. A bitter controversy followed, but in the end the protagonists of the vaccine won when a further trial showed that the vaccine was safe and that it protected four out of five of those vaccinated.


Immunization against viral diseases

Immunization against viral diseases

Immunization against viral diseases (B)

With the exception of smallpox, it was not until well into the 20th century that efficient viral vaccines became available. In fact, it was not until the 1930s that much began to be known about viruses. The two developments that contributed most to the rapid growth in knowledge after that time were the introduction of tissue culture as a means of growing viruses in the laboratory and the availability of the electron microscope. Once the virus could be cultivated with comparative ease in the laboratory, the research worker could study it with care and evolve methods for producing one of the two requirements for a safe and effective vaccine: either a virus that was so attenuated, or weakened, that it could not produce the disease for which it was responsible in its normally virulent form; or a killed virus that retained the faculty of inducing a protective antibody response in the vaccinated individual.

The first of the viral vaccines to result from these advances was for yellow fever, developed by the microbiologist Max Theiler in the late 1930s. About 1945 the first relatively effective vaccine was produced for influenza; in 1954 American physician Jonas Salk introduced a vaccine for polio; and in 1960 an oral polio vaccine, developed by virologist Albert Sabin, came into wide use.

The vaccines went far toward bringing under control three of the major diseases of the time—although, in the case of influenza, a major complication is the disturbing proclivity of the virus to change its character from one epidemic to another. Even so, sufficient progress was made to reduce the chances that a pandemic such as the influenza pandemic of 1918–19, which killed an estimated 25 million people, would occur again. Medical centres were equipped to monitor outbreaks of influenza worldwide in order to establish the identity of the responsible viruses and, if necessary, take steps to produce appropriate vaccines.

During the 1960s effective vaccines came into use for measles and rubella (German measles). Both evoked a certain amount of controversy. In the case of measles in the Western world, it was contended that, if acquired in childhood, measles is not a particularly hazardous malady, and the naturally acquired disease evokes permanent immunity in the vast majority of cases. Conversely, the original vaccine induced a certain number of adverse reactions, and the duration of the immunity it produced was problematic. In 1968 an improved measles vaccine was developed. By 2000 measles was eliminated from the United States. Subsequent lapses in vaccination, however, resulted in its reemergence.

The situation with rubella vaccination was different. This is a fundamentally mild affliction, and the only cause for anxiety is its proclivity to induce congenital deformities if a pregnant woman should acquire the disease. Once an effective vaccine was available, the problem was the extent to which it should be used. Ultimately, consensus was reached that all girls who had not already had the disease should be vaccinated at about 12 years of age. In the United States children are routinely immunized against measles, mumps, and rubella at the age of 15 months.


The immune response

The immune response

The immune response (B)

With advances in cell biology in the second half of the 20th century came a more profound understanding of both normal and abnormal conditions in the body. Electron microscopy enabled observers to peer more deeply into the structures of the cell, and chemical investigations revealed clues to their functions in the cell’s intricate metabolism. The overriding importance of the nuclear genetic material DNA (deoxyribonucleic acid) in regulating the cell’s protein and enzyme production lines became evident. A clearer comprehension also emerged of the ways in which the cells of the body defend themselves by modifying their chemical activities to produce antibodies against injurious agents.

Up until the 20th century, immunity referred mostly to the means of resistance of an animal to invasion by a parasite or microorganism. About the mid-20th century, however, there arose a growing realization that immunity and immunology cover a much wider field and are concerned with mechanisms for preserving the integrity of the individual. The introduction of organ transplantation, with its dreaded complication of tissue rejection, brought this broader concept of immunology to the fore.

At the same time, research workers and clinicians began to appreciate the far-reaching implications of immunity in relation to endocrinology, genetics, tumour biology, and the biology of a number of other maladies. The so-called autoimmune diseases were found to be caused by an aberrant series of immune responses by which the body’s own cells are attacked. Suspicion grew that a number of major disorders, such as diabetes, rheumatoid arthritis, and multiple sclerosis, were associated with similar mechanisms.

In some conditions viruses were found to invade the genetic material of cells and distort their metabolic processes. Such viruses may lie dormant for many years before becoming active. This was discovered to be the underlying cause of certain cancers, such as primary hepatocellular carcinoma (caused by hepatitis C virus) and adult T-cell leukemia (caused by human T-cell lymphotropic virus type I, or HTLV-I). Acquired immune deficiency syndrome (AIDS) was found to be caused by human immunodeficiency virus (HIV), which has a long dormant period and then attacks T cells (immune cells that produce antibodies). The result is that the affected person is not able to generate an immune response to infections or malignancies.



  Immunology (medicine) (B)

Immunology (medicine) (B)

Immunology (medicine) (B)

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 immunity against disease has been known in the West at least since Edward Jenner used cowpox injections to protect people from smallpox in 1796. But the scientific basis for immunology was not established until a century later, when it was recognized that: (1) proliferating microorganisms in the body cause many infectious diseases and (2) the body has certain chemical and cellular components that recognize and destroy foreign substances (antigens) within the body. This new understanding led to highly successful techniques of immunization that could mobilize and stimulate the body’s natural defenses against infectious disease.

It was only in the 20th century, however, that a comprehensive understanding was gained of the formation, mobilization, action, and interaction of antibodies and antigen-reactive lymphocytes, which are the two main active elements of the immune system. Modern immunology, besides using such basic techniques as vaccination, has become increasingly selective and sophisticated in its manipulation of the body’s immune system through drugs and other agents in efforts to achieve a desired therapeutic goal. Immunologic understanding is crucial to the treatment of allergies, which are themselves hypersensitive reactions by the body’s immune system to the presence of harmless antigens such as pollen grains. Immunosuppressive techniques use drugs to suppress the immune system’s tendency to reject and attack antigenic bone grafts and organ transplants that have been medically introduced into the host tissue. Immunology also encompasses the increasingly important study of autoimmune diseases, in which the body’s immune system attacks some constituent of its own tissues as if it were a foreign body. The study of immune deficiencies has become an area of intensive research since the appearance of AIDS (acquired immune deficiency syndrome), a disease that destroys the body’s immune system and for which there is currently no cure.




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