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Overnutrition is associated with diseases such as diabetes and obesity , which are known to affect immune function. More moderate malnutrition, as well as certain specific trace mineral and nutrient deficiencies, can also compromise the immune response. Foods rich in certain fatty acids may foster a healthy immune system.
The immune system, particularly the innate component, plays a decisive role in tissue repair after an insult. The plasticity of immune cells and the balance between pro-inflammatory and anti-inflammatory signals are crucial aspects of efficient tissue repair. According to one hypothesis, organisms that can regenerate could be less immunocompetent than organisms that cannot regenerate.
The immune system is a remarkably effective structure that incorporates specificity, inducibility and adaptation. Failures of host defense do occur, however, and fall into three broad categories: immunodeficiencies, autoimmunity, and hypersensitivities. Immunodeficiencies occur when one or more of the components of the immune system are inactive. The ability of the immune system to respond to pathogens is diminished in both the young and the elderly , with immune responses beginning to decline at around 50 years of age due to immunosenescence.
Additionally, the loss of the thymus at an early age through genetic mutation or surgical removal results in severe immunodeficiency and a high susceptibility to infection. Immunodeficiencies can also be inherited or ' acquired'. AIDS and some types of cancer cause acquired immunodeficiency.
Overactive immune responses comprise the other end of immune dysfunction, particularly the autoimmune disorders. Here, the immune system fails to properly distinguish between self and non-self, and attacks part of the body. Under normal circumstances, many T cells and antibodies react with "self" peptides. Hypersensitivity is an immune response that damages the body's own tissues. Type I hypersensitivity is an immediate or anaphylactic reaction, often associated with allergy. Symptoms can range from mild discomfort to death. Type I hypersensitivity is mediated by IgE , which triggers degranulation of mast cells and basophils when cross-linked by antigen.
This is also called antibody-dependent or cytotoxic hypersensitivity, and is mediated by IgG and IgM antibodies. Type IV reactions are involved in many autoimmune and infectious diseases, but may also involve contact dermatitis poison ivy. These reactions are mediated by T cells , monocytes , and macrophages. Inflammation is one of the first responses of the immune system to infection,  but it can appear without known cause.
The immune response can be manipulated to suppress unwanted responses resulting from autoimmunity, allergy, and transplant rejection , and to stimulate protective responses against pathogens that largely elude the immune system see immunization or cancer. Immunosuppressive drugs are used to control autoimmune disorders or inflammation when excessive tissue damage occurs, and to prevent transplant rejection after an organ transplant.
Anti-inflammatory drugs are often used to control the effects of inflammation. Glucocorticoids are the most powerful of these drugs; however, these drugs can have many undesirable side effects , such as central obesity , hyperglycemia , osteoporosis , and their use must be tightly controlled.
Cytotoxic drugs inhibit the immune response by killing dividing cells such as activated T cells. However, the killing is indiscriminate and other constantly dividing cells and their organs are affected, which causes toxic side effects. Cancer immunotherapy covers the medical ways to stimulate the immune system to attack cancer tumours.
Long-term active memory is acquired following infection by activation of B and T cells. Active immunity can also be generated artificially, through vaccination. The principle behind vaccination also called immunization is to introduce an antigen from a pathogen in order to stimulate the immune system and develop specific immunity against that particular pathogen without causing disease associated with that organism.
With infectious disease remaining one of the leading causes of death in the human population, vaccination represents the most effective manipulation of the immune system mankind has developed. Most viral vaccines are based on live attenuated viruses, while many bacterial vaccines are based on acellular components of micro-organisms, including harmless toxin components. Another important role of the immune system is to identify and eliminate tumors.
This is called immune surveillance. The transformed cells of tumors express antigens that are not found on normal cells. To the immune system, these antigens appear foreign, and their presence causes immune cells to attack the transformed tumor cells. The antigens expressed by tumors have several sources;  some are derived from oncogenic viruses like human papillomavirus , which causes cervical cancer ,  while others are the organism's own proteins that occur at low levels in normal cells but reach high levels in tumor cells.
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One example is an enzyme called tyrosinase that, when expressed at high levels, transforms certain skin cells e. The main response of the immune system to tumors is to destroy the abnormal cells using killer T cells, sometimes with the assistance of helper T cells. This allows killer T cells to recognize the tumor cell as abnormal. Clearly, some tumors evade the immune system and go on to become cancers. Paradoxically, macrophages can promote tumor growth  when tumor cells send out cytokines that attract macrophages, which then generate cytokines and growth factors such as tumor-necrosis factor alpha that nurture tumor development or promote stem-cell-like plasticity.
This limits the effectiveness of drugs based on larger peptides and proteins which are typically larger than Da.
In some cases, the drug itself is not immunogenic, but may be co-administered with an immunogenic compound, as is sometimes the case for Taxol. Computational methods have been developed to predict the immunogenicity of peptides and proteins, which are particularly useful in designing therapeutic antibodies, assessing likely virulence of mutations in viral coat particles, and validation of proposed peptide-based drug treatments.
Early techniques relied mainly on the observation that hydrophilic amino acids are overrepresented in epitope regions than hydrophobic amino acids;  however, more recent developments rely on machine learning techniques using databases of existing known epitopes, usually on well-studied virus proteins, as a training set. It is likely that a multicomponent, adaptive immune system arose with the first vertebrates , as invertebrates do not generate lymphocytes or an antibody-based humoral response. Immune systems appear even in the structurally most simple forms of life, with bacteria using a unique defense mechanism, called the restriction modification system to protect themselves from viral pathogens, called bacteriophages.
Pattern recognition receptors are proteins used by nearly all organisms to identify molecules associated with pathogens. Antimicrobial peptides called defensins are an evolutionarily conserved component of the innate immune response found in all animals and plants, and represent the main form of invertebrate systemic immunity. Ribonucleases and the RNA interference pathway are conserved across all eukaryotes , and are thought to play a role in the immune response to viruses. Unlike animals, plants lack phagocytic cells, but many plant immune responses involve systemic chemical signals that are sent through a plant.
Systemic acquired resistance SAR is a type of defensive response used by plants that renders the entire plant resistant to a particular infectious agent. Evolution of the adaptive immune system occurred in an ancestor of the jawed vertebrates. Many of the classical molecules of the adaptive immune system e.
However, a distinct lymphocyte -derived molecule has been discovered in primitive jawless vertebrates , such as the lamprey and hagfish. These animals possess a large array of molecules called Variable lymphocyte receptors VLRs that, like the antigen receptors of jawed vertebrates, are produced from only a small number one or two of genes. These molecules are believed to bind pathogenic antigens in a similar way to antibodies, and with the same degree of specificity.
The success of any pathogen depends on its ability to elude host immune responses. Therefore, pathogens evolved several methods that allow them to successfully infect a host, while evading detection or destruction by the immune system. These proteins are often used to shut down host defenses. An evasion strategy used by several pathogens to avoid the innate immune system is to hide within the cells of their host also called intracellular pathogenesis.
Here, a pathogen spends most of its life-cycle inside host cells, where it is shielded from direct contact with immune cells, antibodies and complement. Some examples of intracellular pathogens include viruses, the food poisoning bacterium Salmonella and the eukaryotic parasites that cause malaria Plasmodium falciparum and leishmaniasis Leishmania spp.
Other bacteria, such as Mycobacterium tuberculosis , live inside a protective capsule that prevents lysis by complement. Such biofilms are present in many successful infections, e. The mechanisms used to evade the adaptive immune system are more complicated. This is called antigenic variation. An example is HIV, which mutates rapidly, so the proteins on its viral envelope that are essential for entry into its host target cell are constantly changing.
These frequent changes in antigens may explain the failures of vaccines directed at this virus. In HIV, the envelope that covers the virion is formed from the outermost membrane of the host cell; such "self-cloaked" viruses make it difficult for the immune system to identify them as "non-self" structures. Immunology is a science that examines the structure and function of the immune system. It originates from medicine and early studies on the causes of immunity to disease.
The earliest known reference to immunity was during the plague of Athens in BC. 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. Although he explained the immunity in terms of "excess moisture" getting expelled from the blood—therefore preventing the disease to occur for a second time—this theory explained many observations about smallpox known during this time. These and other observations of acquired immunity were later exploited by Louis Pasteur in his development of vaccination and his proposed germ theory of disease.
It was not until Robert Koch 's proofs , for which he was awarded a Nobel Prize in , that microorganisms were confirmed as the cause of infectious disease. Immunology made a great advance towards the end of the 19th century, through rapid developments, in the study of humoral immunity and cellular immunity. 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 the mids, Frank Burnet , inspired by a suggestion made by Niels Jerne ,  formulated the clonal selection theory CST of immunity.
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. From Wikipedia, the free encyclopedia. This is the latest accepted revision , reviewed on 17 September A biological system that protects an organism against disease. Further information: Innate immune system. Main article: Inflammasome. Further information: Granulocyte.
Further information: Inflammation. Further information: Complement system. Further information: Adaptive immune system. Further information: Immunity medical. Further information: Immunodeficiency. Further information: Autoimmunity. Further information: Hypersensitivity. Further information: Immune-mediated inflammatory diseases. Main articles: Immunotherapy and Vaccination. Further information: Cancer immunology. Further information: History of immunology.
Immunologically Active Peptides | SpringerLink
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