Tolerance

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Tolerance or toleration is the state of tolerating, or putting up with, conditionally.

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<span class="mw-page-title-main">Immune system</span> Biological system protecting an organism against disease

The immune system is a network of biological systems that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to parasitic worms, as well as cancer cells and objects such as wood splinters, distinguishing them from the organism's own healthy tissue. Many species have two major subsystems of the immune system. The innate immune system provides a preconfigured response to broad groups of situations and stimuli. The adaptive immune system provides a tailored response to each stimulus by learning to recognize molecules it has previously encountered. Both use molecules and cells to perform their functions.

<span class="mw-page-title-main">Autoimmunity</span> Immune response against an organisms own healthy cells

In immunology, autoimmunity is the system of immune responses of an organism against its own healthy cells, tissues and other normal body constituents. Any disease resulting from this type of immune response is termed an "autoimmune disease". Prominent examples include celiac disease, diabetes mellitus type 1, Henoch–Schönlein purpura, systemic lupus erythematosus, Sjögren syndrome, eosinophilic granulomatosis with polyangiitis, Hashimoto's thyroiditis, Graves' disease, idiopathic thrombocytopenic purpura, Addison's disease, rheumatoid arthritis, ankylosing spondylitis, polymyositis, dermatomyositis, and multiple sclerosis. Autoimmune diseases are very often treated with steroids.

<span class="mw-page-title-main">Toleration</span> Allowing or permitting a thing, person, or idea of which one disapproves

Toleration is when one allows or permits an action, idea, object, or person that they dislike or disagree with.

<span class="mw-page-title-main">Psychrophile</span> Organism capable of growing and reproducing in the cold

Psychrophiles or cryophiles are extremophilic organisms that are capable of growth and reproduction in low temperatures, ranging from −20 °C (−4 °F) to 20 °C (68 °F). They are found in places that are permanently cold, such as the polar regions and the deep sea. They can be contrasted with thermophiles, which are organisms that thrive at unusually high temperatures, and mesophiles at intermediate temperatures. Psychrophile is Greek for 'cold-loving', from Ancient Greek ψυχρός (psukhrós) 'cold, frozen'.

<span class="mw-page-title-main">Adaptive immune system</span> Subsystem of the immune system

The adaptive immune system, also known as the acquired immune system, or specific immune system is a subsystem of the immune system that is composed of specialized, systemic cells and processes that eliminate pathogens or prevent their growth. The acquired immune system is one of the two main immunity strategies found in vertebrates.

Alloimmunity is an immune response to nonself antigens from members of the same species, which are called alloantigens or isoantigens. Two major types of alloantigens are blood group antigens and histocompatibility antigens. In alloimmunity, the body creates antibodies against the alloantigens, attacking transfused blood, allotransplanted tissue, and even the fetus in some cases. Alloimmune (isoimmune) response results in graft rejection, which is manifested as deterioration or complete loss of graft function. In contrast, autoimmunity is an immune response to the self's own antigens. Alloimmunization (isoimmunization) is the process of becoming alloimmune, that is, developing the relevant antibodies for the first time.

Immunopathology is a branch of medicine that deals with immune responses associated with disease. It includes the study of the pathology of an organism, organ system, or disease with respect to the immune system, immunity, and immune responses. In biology, it refers to damage caused to an organism by its own immune response, as a result of an infection. It could be due to mismatch between pathogen and host species, and often occurs when an animal pathogen infects a human.

Immune tolerance, also known as immunological tolerance or immunotolerance, refers to the immune system's state of unresponsiveness to substances or tissues that would otherwise trigger an immune response. It arises from prior exposure to a specific antigen and contrasts the immune system's conventional role in eliminating foreign antigens. Depending on the site of induction, tolerance is categorized as either central tolerance, occurring in the thymus and bone marrow, or peripheral tolerance, taking place in other tissues and lymph nodes. Although the mechanisms establishing central and peripheral tolerance differ, their outcomes are analogous, ensuring immune system modulation.

Molecular mimicry is the theoretical possibility that sequence similarities between foreign and self-peptides are enough to result in the cross-activation of autoreactive T or B cells by pathogen-derived peptides. Despite the prevalence of several peptide sequences which can be both foreign and self in nature, just a few crucial residues can activate a single antibody or TCR. This highlights the importance of structural homology in the theory of molecular mimicry. Upon activation, these "peptide mimic" specific T or B cells can cross-react with self-epitopes, thus leading to tissue pathology (autoimmunity). Molecular mimicry is one of several ways in which autoimmunity can be evoked. A molecular mimicking event is more than an epiphenomenon despite its low probability, and these events have serious implications in the onset of many human autoimmune disorders.

Antigenic variation or antigenic alteration refers to the mechanism by which an infectious agent such as a protozoan, bacterium or virus alters the proteins or carbohydrates on its surface and thus avoids a host immune response, making it one of the mechanisms of antigenic escape. It is related to phase variation. Antigenic variation not only enables the pathogen to avoid the immune response in its current host, but also allows re-infection of previously infected hosts. Immunity to re-infection is based on recognition of the antigens carried by the pathogen, which are "remembered" by the acquired immune response. If the pathogen's dominant antigen can be altered, the pathogen can then evade the host's acquired immune system. Antigenic variation can occur by altering a variety of surface molecules including proteins and carbohydrates. Antigenic variation can result from gene conversion, site-specific DNA inversions, hypermutation, or recombination of sequence cassettes. The result is that even a clonal population of pathogens expresses a heterogeneous phenotype. Many of the proteins known to show antigenic or phase variation are related to virulence.

The eutherian fetoembryonic defense system (eu-FEDS) is a hypothetical model describing a method by which immune systems are capable of recognizing additional states of relatedness like "own species" such as is observed in maternal immune tolerance in pregnancy. The model includes descriptions of the proposed signaling mechanism and several proposed examples of exploitation of this signaling in disease states.

Self-protein refers to all proteins endogenously produced by DNA-level transcription and translation within an organism of interest. This does not include proteins synthesized due to viral infection, but may include those synthesized by commensal bacteria within the intestines. Proteins that are not created within the body of the organism of interest, but nevertheless enter through the bloodstream, a breach in the skin, or a mucous membrane, may be designated as “non-self” and subsequently targeted and attacked by the immune system. Tolerance to self-protein is crucial for overall wellbeing; when the body erroneously identifies self-proteins as “non-self”, the subsequent immune response against endogenous proteins may lead to the development of an autoimmune disease.

<span class="mw-page-title-main">Insect winter ecology</span> Survival strategies of insects during winter

Insect winter ecology describes the overwinter survival strategies of insects, which are in many respects more similar to those of plants than to many other animals, such as mammals and birds. Unlike those animals, which can generate their own heat internally (endothermic), insects must rely on external sources to provide their heat (ectothermic). Thus, insects persisting in winter weather must tolerate freezing or rely on other mechanisms to avoid freezing. Loss of enzymatic function and eventual freezing due to low temperatures daily threatens the livelihood of these organisms during winter. Not surprisingly, insects have evolved a number of strategies to deal with the rigors of winter temperatures in places where they would otherwise not survive.

Certain sites of the mammalian body have immune privilege, meaning they are able to tolerate the introduction of antigens without eliciting an inflammatory immune response. Tissue grafts are normally recognised as foreign antigens by the body and attacked by the immune system. However, in immune privileged sites, tissue grafts can survive for extended periods of time without rejection occurring. Immunologically privileged sites include:

<span class="mw-page-title-main">Autoimmune disease</span> Disorders of adaptive immune system

An autoimmune disease is a condition that results from an anomalous response of the adaptive immune system, wherein it mistakenly targets and attacks healthy, functioning parts of the body as if they were foreign organisms. It is estimated that there are more than 80 recognized autoimmune diseases, with recent scientific evidence suggesting the existence of potentially more than 100 distinct conditions. Nearly any body part can be involved.

Biotic stress is stress that occurs as a result of damage done to an organism by other living organisms, such as bacteria, viruses, fungi, parasites, beneficial and harmful insects, weeds, and cultivated or native plants. It is different from abiotic stress, which is the negative impact of non-living factors on the organisms such as temperature, sunlight, wind, salinity, flooding and drought. The types of biotic stresses imposed on an organism depend the climate where it lives as well as the species' ability to resist particular stresses. Biotic stress remains a broadly defined term and those who study it face many challenges, such as the greater difficulty in controlling biotic stresses in an experimental context compared to abiotic stress.

<span class="mw-page-title-main">Paradox of tolerance</span> Logical paradox in decision-making theory

The paradox of tolerance states that if a society's practice of tolerance includes the intolerant, intolerance will ultimately dominate, eliminating both the tolerant and the practice of tolerance. Karl Popper describes the paradox as arising from the fact that, in order to maintain a tolerant society, the society must retain the right to be intolerant of intolerance.

Ecoimmunology or Ecological Immunology is the study of the causes and consequences of variation in immunity. The field of ecoimmunology seeks to give an ultimate perspective for proximate mechanisms of immunology. This approach places immunology in evolutionary and ecological contexts across all levels of biological organization.

<span class="mw-page-title-main">Tolerance to infections</span>

Tolerance to infection, or disease tolerance, is a mechanism that host organisms can use to fight parasites or pathogens that attack the host. Tolerance is not equivalent to resistance. Disease resistance is the host trait that prevents infection or reduces the number of pathogens and parasites within or on a host.

<span class="mw-page-title-main">Janelle Ayres</span> American immunologist

Janelle S. Ayres is an American immunologist and microbiologist, member of the NOMIS Center for Immunobiology and Microbial Pathogenesis and Helen McLoraine Developmental Chair at the Salk Institute for Biological Sciences. Her research focuses on the relation of host-pathogen interactions with the microbiome.