NationMaster - Encyclopedia: Acquired immune system

The immune system is the system of specialised cells and organs that protect an organism from outside biological influences. In a broad sense, almost every organ has a protective function (e.g., the skin). When the immune system is functioning properly, it protects the body against bacteria and viral infections, destroying cancer cells and foreign substances. If the immune system weakens, its ability to defend the body also weakens, allowing pathogens, including viruses that cause common colds and flu, to grow and flourish in the body. The immune system also performs surveillance of tumor cells, and immune suppression has been reported to increase the risk of certain types of cancer. In biology, an organ is a group of tissues which perform some function. ... A cell is a single unit or compartment, enclosed by a border or wall. ... In biology, an organ (Latin: organum, instrument, tool) is a group of tissues, which perform a specific function or group of functions. ... In biology and ecology, an organism (in Greek organon = instrument) is a complex adaptive system of organs that influence each other in such a way that they function as a more or less stable whole and have properties of life. ... Main articles: Life The most salient example of biological universality is that all living things share a common carbon-based biochemistry and in particular pass on their characteristics via genetic material, which is based on nucleic acids such as DNA and which uses a common genetic code with only minor... Model of the layers of human skin In zootomy and dermatology, skin is an organ of the integumentary system; which is composed of a layer of tissues that protect underlying muscles and organs. ... Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria(singular, bacterium) are a major group of living organisms. ... The HIV virus A virus is a microscopic parasite that infects cells in biological organisms. ... An infection is the detrimental colonization of a host organism by a foreign species. ... For other uses, see Cancer (disambiguation). ... A pathogen or infectious agent is a biological agent that causes disease or illness to its host. ... The Common Cold The Common Cold is a fictional character and a villain in Codename: Kids Next Door. ... Negatively stained flu virions. ... When normal cells are damaged or old they undergo apoptosis; cancer cells, however, avoid apoptosis. ...

The immune system is often divided into two sections:

Innate Immunity: Comprised of germ-line encoded components that provide an immediate "first-line" of defense to continuously ward off noxious influences (pathogens);
Adaptive Immunity: The provision of long lasting and specific protection against formerly encountered pathogens, which takes days to develop, achieving specificity through somatic recombination and selection of pathogen (antigen) receptors

1 Structure
2 Disorders of the human immune system
3 Pharmacology
4 See also
5 Further reading

Structure

Most multicellular organisms possess an "innate immune system", generally comprising a set of germ-line encoded receptors to pathogens, that does not change during the lifetime of the organism. Adaptive immunity, in which the responses to pathogens change and develop during the lifetime of an individual, seems to have appeared somewhat abruptly in evolutionary time, with the appearance of chondrichthyes (cartilaginous or jawed fish). This timeline outlines the major events in the development of life on planet Earth. ... Orders see text The Chondrichthyes or cartilaginous fishes are jawed fish with paired fins, paired nostrils, scales, two-chambered hearts, and skeletons made of cartilage. ...

Organisms that possess an adaptive immunity also possess an innate immunity, and with many of the mechanisms between the systems being common, it is not always possible to draw a hard and fast boundary between the individual components involved in each, despite the clear difference in operation. Higher vertebrates and all mammals have both an innate and an adaptive immune system. Groups Conodonta Hyperoartia Petromyzontidae (lampreys) Pteraspidomorphi (early jawless fish) Thelodonti Anaspida Cephalaspidomorphi (early jawless fish) Galeaspida Pituriaspida Osteostraci Gnathostomata (jawed vertebrates) Placodermi Chondrichthyes (cartilaginous fish) Acanthodii Osteichthyes (bony fish) Actinopterygii (ray-finned fish) Sarcopterygii (lobe-finned fish) Actinistia (coelacanths) Dipnoi (lungfish) Tetrapoda Amphibia Amniota Sauropsida/(Reptiles) Aves (Birds) Synapsida Mammalia... Orders Subclass Multituberculata (extinct) Plagiaulacida Cimolodonta Subclass Palaeoryctoides (extinct) Subclass Triconodonta (extinct) Subclass Eutheria (includes extinct ancestors)/Placentalia (excludes extinct ancestors) Afrosoricida Artiodactyla Carnivora Cetacea Chiroptera Cimolesta (extinct) Creodonta (extinct) Condylarthra (extinct) Dermoptera Desmostylia (extinct) Embrithopoda (extinct) Hyracoidea Insectivora Lagomorpha Litopterna (extinct) Macroscelidea Mesonychia (extinct) Notoungulata (extinct) Perissodactyla Pholidota Plesiadapiformes...

Innate immune system

The adaptive immune system may take days or weeks, after an initial infection, to have an effect. However, most organisms are under constant assault from pathogens, which must be kept in check by the faster-acting innate immune system. Innate immunity defends against pathogens by rapid responses coordinated through "innate" receptors that recognize a wide spectrum of conserved pathogenic components. Plants and many lower animals do not possess an adaptive immune system, and rely instead on their innate immunity. Divisions Land plants (embryophytes) Non-vascular plants (bryophytes) Marchantiophyta - liverworts Anthocerotophyta - hornworts Bryophyta - mosses Vascular plants (tracheophytes) Lycopodiophyta - clubmosses Equisetophyta - horsetails Pteridophyta - true ferns Psilotophyta - whisk ferns Ophioglossophyta - adderstongues Seed plants (spermatophytes) â€ Pteridospermatophyta - seed ferns Pinophyta - conifers Cycadophyta - cycads Ginkgophyta - ginkgo Gnetophyta - gnetae Magnoliophyta - flowering plants Adiantum pedatum (a...

The study of the innate immune system has recently flourished. Earlier studies of innate immunity utilized model organisms that lack adaptive immunity, such as the plant Arabidopsis thaliana, the fly Drosophila melanogaster, and the worm Caenorhabditis elegans. Recent advances have been made in the field of innate immunology with the discovery of toll-like receptors (TLRs) and the intracellular nucleotide-binding site leucine-rich repeat proteins (NODs), which are receptors in mammal cells that are responsible for a large proportion of the innate immune recognition of pathogens. Binomial name Arabidopsis thaliana (L.) Heynh. ... Binomial name Drosophila melanogaster Meigen, 1830 dorsal view Drosophila melanogaster (Black-bellied Dew-lover) a dipteran (two-winged) insect, is the species of fruit fly that is commonly used in genetic experiments; it is among the most important model organisms. ... Binomial name Caenorhabditis elegans Maupas, 1900 Caenorhabditis elegans (pronounced see-no-rab-DYE-tis) is a free-living nematode (a roundworm), about 1 mm in length, which lives in a temperate soil environment. ... Toll-like receptors (TLRs) are type I transmembrane proteins that serve as a key part of the innate immune system. ...

In 1989, prior to the discovery of mammalian TLRs, Charles Janeway conceptualized and proposed that evolutionarily conserved features of infectious organisms were detected by the immune system through a set of specialized receptors, which he termed pathogen-associated molecular patterns (PAMPs) and pattern recognition receptors (PRRs), respectively. This was a remarkable insight at the time but was only fully appreciated after the discovery of TLRs. The TLRs now comprise the largest family of innate immune receptors (or PRRs). Janeway’s hypothesis has come to be known as the ‘stranger model’ and substantial debate in the field persists to this day as to whether or not the concept of PAMPs and PRRs, as described by Janeway, is truly suitable to describe the mechanisms of innate immunity. The competing ‘danger model’ was proposed in 1994 by Polly Matzinger and argues against the focus of the stranger model on microbial derived signals, suggesting instead that endogenous danger/alarm signals from distressed tissues serve as the principle purveyors of innate immune responses. Charles Alderson Janeway, Jr. ...

Both models are supported in the current literature, with discoveries that substances of both microbial and non-microbial sources are able to stimulate innate immune responses, which has led to increasing awareness that perhaps a blend of the two models would best serve to describe the currently known mechanisms governing innate immunity.

First-line defense: Physical barrier

The first-line defense includes barriers to infection, such as skin and mucus coating of the gut and airways, physically preventing the interaction between the host and the pathogen. Pathogens, which penetrate these barriers, encounter constitutively-expressed anti-microbial molecules (eg. lysozyme) that restrict the infection. Model of the layers of human skin In zootomy and dermatology, skin is an organ of the integumentary system; which is composed of a layer of tissues that protect underlying muscles and organs. ... Mucus is a slippery secretion of the lining of various membranes in the body (mucous membranes). ... For the Physics term GUT, please refer to Grand unification theory The gastrointestinal or digestive tract, also referred to as the GI tract or the alimentary canal or the gut, is the system of organs within multicellular animals which takes in food, digests it to extract energy and nutrients, and... For the aerial route, see Airway (aviation). ... Lysozyme 3D structure. ...

Second-line defense: Phagocytic cells

The second-line defense includes phagocytic cells (macrophages and neutrophil granulocytes) that can engulf (phagocytose) foreign substances. Macrophages are thought to mature continuously from circulating monocytes. A phagocyte is a cell that ingests (and destroys) foreign matter, such as microorganisms or debris via a process known as phagocytosis, in which these cells ingest and kill offending cells by cellular digestion. ... Macrophages (Greek: big eaters) are cells found in tissues that are responsible for phagocytosis of pathogens, dead cells and cellular debris. ... Neutrophil granulocytes (commonly referred to as neutrophils) are a class of white blood cells and are part of the immune system. ... Phagocytosis (literally, cell eating) is a form of endocytosis where large particles are enveloped by the cell membrane of a (usually larger) cell and internalized to form a phagosome, or food vacuole. ... A monocyte is a leukocyte, part of the human bodys immune system that protect against blood-borne pathogens and move quickly to sites of infection in the tissues. ...

Phagocytosis involves chemotaxis, where phagocytic cells are attracted to microorganisms by means of chemotactic chemicals such as microbial products, complement, damaged cells and white blood cell fragments. Chemotaxis is followed by adhesion, where the phagocyte sticks to the microorganism. Adhesion is enhanced by opsonization, where proteins like opsonins are coated on the surface of the bacterium. This is followed by ingestion, in which the phagocyte extends projections, forming pseudopods that engulf the foreign organism. Finally, the bacterium is digested by the enzymes in the lysosome, involving reactive oxygen species and proteases. Chemotaxis is the phenomenon in which bodily cells, bacteria, and other single-celled or multicellular organisms direct their movements according to certain chemicals in their environment. ... White blood cells (also called leukocytes or immune cells) are a component of blood. ... Schematic of cell adhesion The study of cell adhesion is part of cell biology. ... An opsonin is any molecule that acts as a binding enhancer for the process of phagocytosis. ... An opsonin is any molecule that acts as a binding enhancer for the process of phagocytosis. ... Pseudopods or pseudopodia (false feet) are temporary projections of eukaryotic cells. ... Lysosomes contain digestive enzymes (acid hydrolases) to digest macromolecules. ... Reactive oxygen species (ROS) include oxygen ions, free radicals and peroxides both inorganic and organic. ... Proteases (proteinases, peptidases or proteolytic enzymes) are enzymes that break peptide bonds between amino acids of proteins. ...

Anti-microbial proteins

In addition, anti-microbial proteins may be activated if a pathogen passes through the barrier offered by skin. There are several classes of antimicrobial proteins, such as acute phase proteins (C-reactive protein, for example, enhances phagocytosis and activates complement when it binds itself to the C-protein of S. pneumoniae ), lysozyme, and the complement system. Acute phase proteins are a class of proteins that are synthetized in the liver in response to inflammation. ... C-reactive protein (CRP) is a plasma protein, an acute phase protein produced by the liver. ... Binomial name Streptococcus pneumoniae (Klein 1884) Chester 1901 Streptococcus pneumoniae is a species of Streptococcus that is a major human pathogen. ... Lysozyme 3D structure. ... The complement system is a complex biochemical cascade of the immune system, leading to cytolysis, chemotaxis, opsonization and inflammation, it can mark pathogens for phagocytosis. ...

The complement system is a very complex group of serum proteins which is activated in a cascade fashion. Three different pathways are involved in complement activation: The complement system is a complex biochemical cascade of the immune system, leading to cytolysis, chemotaxis, opsonization and inflammation, it can mark pathogens for phagocytosis. ... A cascade is a term for a waterfall, or series of waterfalls, and is applied abstractly to many different concepts involving a series of steps or effects that follow one after the other. ...

classical pathway: recognizes antigen-antibody complexes;
alternative pathway: spontaneously activates on contact with pathogenic cell surfaces; and
mannose-binding lectin pathway: recognizes mannose sugars, which tend to appear only on pathogenic cell surfaces.

A cascade of protein activity follows complement activation; this cascade can result in a variety of effects, including opsonization of the pathogen, destruction of the pathogen by the formation and activation of the membrane attack complex, and inflammation. This article may be too technical for most readers to understand. ... The alternative pathway of the complement system is a humoral component of the immune systems natural defence against infections which can operate without antibody participation. ... Mannose is a sugar, one of the hexose series of carbohydrates. ... An opsonin is any molecule that acts as a binding enhancer for the process of phagocytosis. ... Inflammation is the first response of the immune system to infection or irritation and may be referred to as the innate cascade. ...

Adaptive immune system

The adaptive immune system, also called the "acquired immune system", ensures that most mammals that survive an initial infection by a pathogen are generally immune to further illness, caused by that same pathogen. The adaptive immune system is based on dedicated immune cells termed leukocytes (white blood cells) that are produced by stem cells in the bone marrow, and mature in the thymus and/or lymph nodes. In many species, including mammals, the adaptive immune system can be divided into two major sections: White Blood Cells is also the name of a White Stripes album. ... Mouse embryonic stem cells. ... Bone marrow (or medulla ossea) is the tissue comprising the center of large bones. ... In human anatomy, the thymus is a ductless gland located in the upper anterior portion of the chest cavity. ... Structure of the lymph node. ... Orders Subclass Monotremata Monotremata Subclass Marsupialia Didelphimorphia Paucituberculata Microbiotheria Dasyuromorphia Peramelemorphia Notoryctemorphia Diprotodontia Subclass Placentalia Xenarthra Dermoptera Desmostylia Scandentia Primates Rodentia Lagomorpha Insectivora Chiroptera Pholidota Carnivora Perissodactyla Artiodactyla Cetacea Afrosoricida Macroscelidea Tubulidentata Hyracoidea Proboscidea Sirenia The mammals are the class of vertebrate animals primarily characterized by the presence of mammary...

Humoral immune system: It acts against bacteria and viruses in the body liquids (eg. blood) by means of proteins, called immunoglobulins (also known as antibodies), which are produced by B cells.
Cellular immune system: It destroys virus-infected cells (among other duties) with T cells (also called "T lymphocytes"; "T" means they develop in the thymus). There are two major types of T cells:
- Cytotoxic T cells (T_C cells): These cells recognize infected cells by using T cell receptors to probe cell surfaces. If they recognize an infected cell, they release granzymes to trigger that cell to become apoptotic ("commit suicide"), thus killing that cell and any viruses that it is in the process of creating.
- Helper T cells (T_H cells): These cells activate macrophages (cells that ingest dangerous material), and also produce cytokines (interleukins) that induce the proliferation of B and T cells.

In addition, there are regulatory T cells (T_reg cells) which are important in regulating cell-mediated immunity. Humoral immunity is mediated by secreted antibodies, produced in the cells of the B lymphocyte lineage (B cell). ... Red blood cells (erythrocytes) are present in the blood and help carry oxygen to the rest of the cells in the body Blood is a circulating tissue composed of fluid plasma and cells (red blood cells, white blood cells, platelets). ... Schematic of antibody binding to an antigen An antibody is a protein complex used by the immune system to identify and neutralize foreign objects like bacteria and viruses. ... Schematic of antibody binding to an antigen An antibody is a protein used by the immune system to identify and neutralize foreign objects like bacteria and viruses. ... B cells are lymphocytes that play a large role in the humoral immune response (as opposed to the cell-mediated immune response). ... Cell-mediated immunity is an immune response that does not involve antibodies but rather involves the activation of macrophages and NK-cells, the production of antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen. ... T cells are a subset of lymphocytes that play a large role in the immune response. ... In human anatomy, the thymus is a ductless gland located in the upper anterior portion of the chest cavity. ... A cytotoxic (or TC) T cell is a T cell (a type of white blood cell) which has on its surface antigen receptors that can bind to fragments of antigens displayed by the Class I MHC molecules of virus infected somatic cells and tumor cells. ... The T cell receptor or TCR is responsible for recognizing antigen bound to MHC. It is a heterodimer usually of an alpha and beta chain (though TCRs with gamma-delta chains exist as well). ... Granzymes are exogenous serine proteases that are released by cytoplasmic granules within cytotoxic T cells and natural killer cells. ... Apoptosis In biology, apoptosis (from the Greek words apo = from and ptosis = falling, pronounced ap-a-tow-sis[1]) is one of the main types of programmed cell death (PCD). ... A helper (or TH) T cell is a T cell (a type of white blood cell) which has on its surface antigen receptors that can bind to fragments of antigens displayed by the Class II MHC molecules found on professional antigen-presenting cells (APCs). ... Macrophages (Greek: big eaters) are cells found in tissues that are responsible for phagocytosis of pathogens, dead cells and cellular debris. ... Cytokines are small protein molecules that are the core of communication between immune system cells, and even between these cells and cells belonging to other tissue types. ... Interleukins are a group of cytokines that are expressed by white blood cells (leukocytes, hence the -leukin) as a means of communication (inter-). The function of the immune system depends in a large part on interleukins, and rare deficiencies of a number of them have been described, all featuring autoimmune... The term cell growth is used in two different ways in biology. ... Regulatory T cells (also known as suppressor T cells) are a specialized subpopulation of T cells that act to suppress activation of the immune system and thereby maintain immune system homeostasis and tolerance to self. ...

Intersections between systems

Splitting the innate and adaptive immunity has served to simplify discussions of immunology. However, the systems are quite intertwined in a number of important respects.

One of the most important examples are the mechanisms of 'antigen presentation'. After they leave the thymus, T cells require activation to proliferate and differentiate into cytotoxic ("killer") T cells (CTLs). Activation is provided by antigen-presenting cells (APCs), a major category of which are the dendritic cells. These cells are part of the innate immune system. An antigen presenting cell (APC) is a cell that displays foreign antigen complexed with MHC on its surface. ... Dendritic cells (DC) are immune cells and form part of the mammal immune system. ...

Activation occurs when a dendritic cell simultaneously binds itself to a T "helper" cell's antigen receptor and to its CD28 receptor, which provides the "second signal" needed for DC activation. This signal is a means by which the dendritic cell conveys that the antigen is indeed dangerous, and that the next encountered T "killer" cells need to be activated. This mechanism is based on antigen-danger evaluation by the T cells that belong to the adaptive immune system. But the dendritic cells are often directly activated by engaging their toll-like receptors, getting their "second signal" directly from the antigen. In this way, they actually recognize in "first person" the danger, and direct the T killer attack. In this respect, the innate immune system therefore plays a critical role in the activation of the adaptive immune system. Dendritic cells (DC) are immune cells and form part of the mammal immune system. ... Toll-like receptors (TLRs) are type I transmembrane proteins that serve as a key part of the innate immune system. ...

Adjuvants, or chemicals that stimulate an immune response, provide artificially this "second signal" in procedures when an antigen, that would not normally raise an immune response, is artificially introduced into a host. With the adjuvant, the response is much more robust. Historically, a commonly-used formula is Freund's Complete Adjuvant, an emulsion of oil and mycobacterium. It was later discovered that toll-like receptors, expressed on innate immune cells, are critical in the activation of adaptive immunity. In medicine, adjuvants are agents which modify the effect of other agents while having few if any direct effects when given by themselves. ... Freunds adjuvant is an antigen solution emulsified in mineral oil, used as an immunopotentiator (booster of the immune system). ... Species see text Mycobacterium is the a genus of actinobacteria, given its own family, the Mycobacteriaceae. ...

Disorders of the human immune system

The most important function of the human immune system occurs at the cellular level of the blood and tissues. The lymphatic and blood circulation systems are highways for specialized white blood cells to travel round the body. White blood cells include B cells, T cells, natural killer cells, and macrophages. Each has a different responsibility, but all function together with the primary objective of recognizing, attacking and destroying bacteria, viruses, cancer cells, and all substances seen as foreign. Without this coordinated effort, a person would not be able to survive more than a few days, before succumbing to overwhelming infection. In mammals including humans, the lymphatic vessels (or lymphatics) are a network of thin tubes that branch, like blood vessels, into tissues throughout the body. ... The circulatory system or cardiovascular system is the organ system which circulates blood around the body of most animals. ... White blood cells (also called leukocytes or immune cells) are a component of blood. ... B cells are lymphocytes that play a large role in the humoral immune response (as opposed to the cell-mediated immune response). ... T cells are a subset of lymphocytes that play a large role in the immune response. ... Natural killer cells (NK) are a type of lymphocyte (a white blood cell) and a component of nonspecific immune defense. ... Macrophages (Greek: big eaters) are cells found in tissues that are responsible for phagocytosis of pathogens, dead cells and cellular debris. ... Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria(singular, bacterium) are a major group of living organisms. ... A common alternate meaning of virus is computer virus. ... When normal cells are damaged or old they undergo apoptosis; cancer cells, however, avoid apoptosis. ...

Infections set off an alarm that alerts the immune system to bring out its defensive weapons. Natural killer cells and macrophages rush to the scene to gobble up and digest infected cells. If the first line of defense fails to control the threat, antibodies, produced by the B cells, upon the order of T helper cells, are custom-designed to hone in on the invader. Wikipedia does not yet have an article with this exact name. ...

Many disorders of the human immune system fall into two broad categories that are characterized by:

Attenuated immune response: There are 'congenital' (inborn) and 'acquired' forms of immunodeficiency, characterized by an attenuated response. Chronic granulomatous disease, in which phagocytes have trouble destroying pathogens, is an example of the former, while AIDS ("Acquired Immune Deficiency Syndrome"), an infectious disease caused by the HIV virus that destroys CD4⁺ T cells, is an example of the latter. Immunosuppressive medication intentionally induces an immunodeficiency in order to prevent rejection of transplanted organs.

Overzealous immune response: On the other end of the scale, an overactive immune system figures in a number of other disorders, particularly autoimmune disorders such as lupus erythematosus, type I diabetes (sometimes called "juvenile onset diabetes"), multiple sclerosis, psoriasis, and rheumatoid arthritis. In these, the immune system fails to properly distinguish between self and non-self, and attacks a part of the patient's own body. Other examples of overzealous immune responses in disease include hypersensitivities, such as allergies and asthma.

Many factors can also contribute to the general weakening of the immune system: In medicine, immune deficiency (or immunodeficiency) is a state where the immune system is incapable of defending the organism from infectious disease. ... In medicine (genetics and pediatrics) chronic granulomatous disease (CGD) is a hereditary disease where neutrophil granulocytes are unable to destroy ingested pathogens. ... A phagocyte is a cell that ingests (and destroys) foreign matter, such as microorganisms or debris via a process known as phagocytosis, in which these cells ingest and kill offending cells by cellular digestion. ... The Red Ribbon is the global symbol for solidarity with HIV-positive people and those living with AIDS. AIDS is an acronym for Acquired Immunodeficiency Syndrome or Acquired Immune Deficiency Syndrome and is defined as a collection of symptoms and infections resulting from the depletion of the immune system caused... In medicine, infectious disease or communicable disease is disease caused by a biological agent (e. ... The human immunodeficiency virus, commonly called HIV, is a retrovirus that primarily infects vital components of the human immune system such as CD4+ T cells, macrophages and dendritic cells. ... Transplant rejection is when the immune system of the recipient of a transplant attacks the transplanted organ or tissue. ... An organ transplant is the transplantation of an organ (or part of one) from one body to another, for the purpose of replacing the recipients damaged or failing organ with a working one from the donor. ... Autoimmune diseases arise from an overactive immune response of the body against substances and tissues normally present in the body. ... Diabetes mellitus is a medical disorder characterized by varying or persistent hyperglycemia (elevated blood sugar levels), especially after eating. ... Rheumatoid arthritis (RA) is a chronic, inflammatory autoimmune disorder that causes the immune system to attack the joints. ... Hypersensitivity is the name given to a state in which an immune response damages the bodys own tissues. ... This article needs cleanup. ...

Poor eating habits, and alcohol abuse;
Drug use (particularly the use of anti-cancer drugs, corticosteroids, and antibiotics);
Radiation;
Exposure to environmental toxins, chemical, cigarette smoke, polluted air; and
Stress (research show that psychological stress can greatly increase your susceptibility to colds, and other viral diseases).

The body's immunity also begins to wear down as a person gets older. This article needs cleanup. ... In physiology, corticosteroids are a class of steroid hormones that are produced in the adrenal cortex. ... An antibiotic is a drug that kills or slows the growth of bacteria. ... Radiation has a variety of different meanings. ... An environment is a complex of external factors. ... A toxin, in a scientific context, is a biologically produced substance that causes injury to the health of a living thing on contact or absorption, typically by interacting with biological macromolecules such as enzymes and receptors. ... A cigarette will burn to ash on one end. ... Smoke from a wildfire Smoke is a suspension in air (aerosol) of small particles resulting from incomplete combustion of a fuel. ... This power plant in New Mexico releases sulfur dioxide and particulate matter into the air. ... Stress (roughly the opposite of relaxation) is a medical term for a wide range of strong external stimuli, both physiological and psychological, which can cause a physiological response called the general adaptation syndrome, first described in 1936 by Hans Selye in the journal Nature. ...

Pharmacology

Despite high hopes, there are no medications that directly increases the activity of the immune system. Various forms of medication that activate the immune system may indeed cause autoimmune disorders. A medication is a licenced drug taken to cure or reduce symptoms of an illness or medical condition. ... Autoimmune diseases arise from an overactive immune response of the body against substances and tissues normally present in the body. ...

Suppression of the immune system is often used to control autoimmune disorders or inflammation when this causes excessive tissue damage, and to prevent transplant rejection after an organ transplant. Commonly used immunosuppressants include glucocorticoids, azathioprine, methotrexate, ciclosporin, cyclophosphamide and mercaptopurine. In organ transplants, ciclosporin, tacrolimus, mycophenolate mofetil and various others are used to prevent organ rejection through selective T cell inhibition. Inflammation is the first response of the immune system to infection or irritation and may be referred to as the innate cascade. ... Transplant rejection is when the immune system of the recipient of a transplant attacks the transplanted organ or tissue. ... An organ transplant is the transplantation of a whole or partial organ from one body to another (or from a donor site on the patients own body), for the purpose of replacing the recipients damaged or failing organ with a working one from the donor site. ... Immunosuppression is the medical suppression of the immune system. ... Glucocorticoids are a class of steroid hormones characterised by an ability to bind with the cortisol receptor and trigger similar effects. ... Azathioprine is a chemotherapy drug, now rarely used for chemotherapy but more for immunosuppression in organ transplantation and autoimmune disease such as rheumatoid arthritis or Crohns disease. ... Methotrexate (abbreviated MTX; formerly known as amethopterin) is an antimetabolite drug used in treatment of cancer and autoimmune disease. ... Ciclosporin (INN), cyclosporine or cyclosporin (former BAN), is an immunosuppressant drug. ... Cyclophosphamide is a nitrogen mustard alkylating agent, used to treat various types of cancer and some autoimmune disorders. ... Mercaptopurine: chemical structure Mercaptopurine (also called 6-MP or by its brand name PurinetholÂ®) is an immunosuppressive drug used to treat leukemia. ... Ciclosporin (INN), cyclosporine or cyclosporin (former BAN), is an immunosuppressant drug. ... Tacrolimus (also FK-506 or Fujimycin) is an immunosuppressive drug. ... Mycophenolate mofetil (MMF, trade name Cellcept®) is an immunosuppresant drug used to prevent rejection in organ transplantation. ...

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