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The adaptive immune system is composed of highly specialized, systemic cells and processes that eliminate pathogenic challenges. The adaptive or specific immune system is activated by the “non-specific” innate immune system. It is the adaptive immune response that provides the immune system with the ability to recognize and remember specific pathogens, and to mount stronger attacks each time the pathogen is encountered. This is adaptive immunity because the body's immune system prepares itself for future challenges. A pathogen or infectious agent is a biological agent that causes disease or illness to its host. ...
The innate immune system is comprised of the cells and mechanisms that defend the host from infection by other organisms, in a non-specific manner. ...
Functions
Adaptive immunity is triggered when a pathogen evades the innate immune system and generates a threshold level of antigen.[1]
The major functions of the adaptive immune system include:
- The recognition of specific “non-self” antigens in the presence of “self”, during the process of antigen presentation.
- The generation of responses that are tailored to maximally eliminate specific pathogens or pathogen infected cells.
- The development of immunological memory, in which each pathogen is “remembered” by a signature antigen. These memory cells can be called upon to quickly eliminate a pathogen should subsequent infections occur.
Effector cells -
The cells of the adaptive immune system are a type of leukocyte, called a lymphocyte. B cells and T cells are the major types of lymphocytes. The human body has about 2 trillion lymphocytes, constituting 20–40% of the body’s WBCs; their total mass is about the same as the brain or liver.[2] The peripheral blood contains 20–50% of circulating lymphocytes; the rest move within the lymphatic system.[2] A lymphocyte is a type of white blood cell involved in the human bodys immune system. ...
Image File history File linksMetadata Download high-resolution version (1946x1788, 1219 KB) Summary Licensing File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Immune system Lymphocyte Metadata This file contains additional information, probably added from the digital camera or...
Image File history File linksMetadata Download high-resolution version (1946x1788, 1219 KB) Summary Licensing File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Immune system Lymphocyte Metadata This file contains additional information, probably added from the digital camera or...
SEM Cambridge S150 at Geological Institute, University Kiel, 1980 SEM opened sample chamber The scanning electron microscope (SEM) is a type of electron microscope capable of producing high resolution images of a sample surface. ...
A lymphocyte is a type of white blood cell involved in the human bodys immune system. ...
A lymphocyte is a type of white blood cell involved in the human bodys immune system. ...
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. ...
In animals, the brain, or encephalon (Greek for in the head), is the control center of the central nervous system. ...
B cells and T cells are derived from the same pluripotential hemopoietic stem cells, and are indistinguishable from one another until after they are activated.[3] B cells play a large role in the humoral immune response, whereas T-cells are intimately involved in cell-mediated immune responses. B-cells may be named for the bursa of Fabricius, an organ unique to birds, where the cells were first found to develop. However, in nearly all other vertebrates, B cells (and T-cells) are produced by stem cells in the bone marrow.[3] T-cells travel to and develop in the thymus, from which they derive their name. In an adult animal, the peripheral lymphoid organs contain a mixture of B- and T cells in (at least) three stages of differentiation: Sketch of bone marrow and its cells Pluripotential hemopoietic stem cells or pluripotential hematopoietic stem cells (PHSCs) are stem cells found in the bone marrow. ...
Humoral immunity is mediated by secreted antibodies, produced in cells of the B lymphocyte lineage (B cell). ...
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. ...
In birds, the bone marrow is the site of hematopoiesis and the bursa of Fabricius (Latin: Bursa cloacalis or Bursa fabricii) is a specialized organ that, as first demonstrated by Bruce Glick and later by Max Cooper and Robert Good, is necessary for B cell development. ...
Orders Many - see section below. ...
Classes and Clades See below Vertebrata is a subphylum of chordates, specifically, those with backbones or spinal columns. ...
- naive cells that have matured, left the bone marrow or thymus, have entered the lymphatic system, but that have yet to encounter their cognate antigen,
- effector cells that have been actived by their cognate antigen, and are actively involved in eliminating a pathogen and,
- memory cells – the long-lived survivors of past infections.
Effector cells are a type of lymphocyte that are actively engaged in secreting antibodies. ...
Memory cell can refer to Memory B cell, a type of biological cell. ...
Antigen presentation -
Adaptive immunity relies on the capacity of immune cells to distinguish between the body's own cells and unwanted invaders. The host’s cells express “self” antigens. These antigens are different from those on the surface of bacteria ("non-self" antigens) or on the surface of virally infected host cells (“missing-self”). The adaptive response is triggered by recognizing non-self and missing-self antigens. Antigen presentation is a process in the bodys immune system by which macrophages, dendritic cells and leukocytes capture antigens and then carry those antigens to T-cells. ...
With the exception of non-nucleated cells (including erythrocytes), all cells are capable of presenting antigen and of activating the adaptive response.[3] Some cells are specially equipped to present antigen, and to prime naive T cells. Dendritic cells and B-cells (and to a lesser extent macrophages) are equipped with special immunostimulatory receptors that allow for enhanced activation of T cells, and are termed professional antigen presenting cells (APC). Human red blood cells Red blood cells are the most common type of blood cell and are the vertebrate bodys principal means of delivering oxygen to body tissues via the blood. ...
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Several T cells subgroups can be activated by professional APCs, and each type of T cell is specially equipped to deal with each unique bacterial, viral pathogen or toxin. The type of T cell activated, and the type of response generated, depends in part, on the context in which the APC first encountered the antigen.[1]
 Antigen presentation stimulates T cells to become either "cytotoxic" CD8+ cells or "helper" CD4+ cells [4]. Image File history File links Antigen_presentation. ...
Image File history File links Antigen_presentation. ...
Exogenous antigens Dendritic cells engulf exogenous (outside the cell) pathogens, such as bacteria, parasites or toxins in the tissues and then migrate, via chemotactic signals, to the T cell enriched lymph nodes. During migration, DCs undergo a process of maturation in which they lose most of their ability to engulf other pathogens and develop an ability to communicate with T-cells. The DC uses enzymes to chop the pathogen into smaller pieces, called antigens. In the lymph node, the DC will display these "non-self" antigens on its surface by coupling them to a "self"-receptor called the Major histocompatibility complex, or MHC (also known in humans as Human leukocyte antigen (HLA)).[1] This MHC:antigen complex is recognized by T-cells passing through the lymph node. Exogenous antigens are usually displayed on MHC Class II molecules, which activate CD4+ helper T-cells.[1] enrich eNRICH a web-based fully customisable software for knowledge management to find users information or knowledge available on the Internet and to create relevant content of their own. ...
Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ...
An antigen is a substance that stimulates an immune response, especially the production of antibodies. ...
MHC I (1hsa) vs MHC II (1dlh) (more details. ...
The human leukocyte antigen system (sometimes human lymphocyte antigen) (HLA) is the general name of a group of genes in the human major histocompatibility complex (MHC) region on human chromosome 6 (mouse chromosome 17) that encodes the cell-surface antigen-presenting proteins. ...
The major histocompatibility complex (MHC) is a large genomic region or gene family found in most vertebrates. ...
Endogenous antigens Endogenous antigens (from inside the cell) are produced by viruses replicating within a host cell.[1] The host cells use enzymes to digest virally associated proteins, and displays these pieces on its surface to T-cells by coupling them to MHC. Endogenous antigens are typically displayed on MHC Class I molecules, and activate CD8+ cytotoxic T-cells. With the exception of non-nucleated cells (including erythrocytes), Class I MHC is expressed by all host cells.[1] Human red blood cells Red blood cells are the most common type of blood cell and are the vertebrate bodys principal means of delivering oxygen to body tissues via the blood. ...
CD8+ T lymphocytes and cytotoxicity -
Cytotoxic T cells (also known as TC, killer T cell, or cytotoxic T-lymphocyte (CTL)) are a sub-group of T cells which induce the death of cells that are infected with viruses (and other pathogens), or are otherwise damaged or dysfunctional[1]. A cytotoxic (or TC) T cell is a T cell (a type of white blood cell) which has on its surface antigen receptors called T-cell receptors (TCRs) that can bind to fragments of antigens displayed by the Class I MHC molecules of virus (or other intracellular pathogen) infected somatic...
 Killer T cells—also called cytotoxic T lymphocytes or CTL-directly attack other cells carrying certain foreign or abnormal molecules on their surfaces [4]. Naive cytotoxic T cells are activated when their T-cell receptor (TCR) strongly interacts with a peptide-bound MHC class I molecule. This affinity depends on the type and orientation of the antigen/MHC complex, and is what keeps the CTL and infected cell bound together.[1] Once activated the CTL undergoes a process called clonal expansion in which it gains functionality, and divides rapidly, to produce an army “armed”-effector cells. Activated CTL will then travel throughout the body in search of cells bearing that unique MHC Class I + peptide. Image File history File links Cytotoxic_T_cell. ...
Image File history File links Cytotoxic_T_cell. ...
When exposed to these infected or dysfunctional somatic cells, effector CTL release perforin and granulysin: cytotoxins which form pores in the target cell's plasma membrane, allowing ions and water to flow into the infected cell, and causing it to burst or lyse.[1] CTL release granzyme, a serine protease that enters cells via pores to induce apoptosis (cell death). To limit extensive tissue damage during an infection, CTL activation is tightly controlled and generally requires a very strong MHC/antigen activation signal, or additional activation signals provided by "helper" T-cells (see below).[1] A somatic cell is generally taken to mean any cell forming the body of an organism: the word somatic is derived from the Greek word sÅma, meaning body. Somatic cells, by definition, are not germline cells . ...
Perforin is a cytolytic protein found in the granules of CD8 T-cells and NK cells. ...
Drawing of a cell membrane A component of every biological cell, the cell membrane (or plasma membrane) is a thin and structured bilayer of phospholipid and protein molecules that envelopes the cell. ...
An ion is an atom or group of atoms that normally are electrically neutral and achieve their status as an ion by loss (or addition) of an electron(s). ...
Lysis (Greek lusis from luein = to separate) is the reduction of symptoms of a disease the dissolving of cells osmotic lysis chemical lysis viral lysis a dialogue of Plato about friendship (philia) This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the...
Granzymes are exogenous serine proteases that are released by cytoplasmic granules within cytotoxic T cells and natural killer cells. ...
In biochemistry, serine proteases or serine endopeptidases (newer name) are a class of peptidases (enzymes that cleave peptide bonds in proteins) that are characterised by the presence of a serine residue in the active center of the enzyme. ...
A cell undergoing apoptosis. ...
Upon resolution of the infection, most of the effector cells will die and be cleared away by phagocytes, but a few of these cells will be retained as memory cells.[3] Upon a later encounter with the same antigen, these memory cells quickly differentiate into effector cells, dramatically shortening the time required to mount an effective response.
CD4+ “helper” T-cells -
 The T lymphocyte activation pathway. T cells contribute to immune defenses in two major ways: some direct and regulate immune responses; others directly attack infected or cancerous cells [4]. CD4+ Lymphocytes, or helper T cells, are immune response mediators, and play an important role in establishing and maximizing the capabilities of the adaptive immune response.[1] These cells have no cytotoxic or phagocytic activity; and cannot kill infected cells or clear pathogens, but, in essence "manage" the immune response, by directing other cells to perform these tasks. T helper cells (also known as effector T cells or Th cells) are a sub-group of lymphocytes (a type of white blood cell or leukocyte) that play an important role in establishing and maximising the capabilities of the immune system. ...
Image File history File links Download high-resolution version (600x907, 111 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Immune system T cell ...
Image File history File links Download high-resolution version (600x907, 111 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Immune system T cell ...
Helper T cells express T-cell receptors (TCR) that recognize antigen bound to Class II MHC molecules. The activation of a naive helper T-cell causes it to release cytokines, which influences the activity of many cell types, including the APC that activated it. Helper T-cells require a much milder activation stimulus than cytotoxic T-cells. Helper T-cells can provide extra signals that "help" activate cytotoxic cells.[3]
Th1 and Th2: helper T cell responses Two types of effector CD4+ T helper cell responses can be induced by a professional APC, designated Th1 and Th2, each designed to eliminate different types of pathogens. The factors that dictate whether an infection will trigger a Th1 or Th2 type response are not fully understood, but the response generated does play an important role in the clearance of different pathogens.[1]
The Th1 response is characterized by the production of Interferon-gamma, which activates the bactericidal activities of macrophages, and induces B-cells to make opsonizing (coating) antibodies, and leads to "cell-mediated immunity" [1]. The Th2 response is characterized by the release of Interleukin 4, which results in the activation of B-cells to make neutralizing (killing) antibodies, leading to "humoral immunity".[1] Generally, Th1 responses are more effecitve against intracellular pathogens (viruses and bacteria that are inside host cells), while Th2 responses are more effective against extracellular bacteria, parasites and toxins[1]. Like cytotoxic T-cells, most of the CD4+ helper cells will die upon resolution of infection, with a few remaining as CD4+ memory cells. Interferon-gamma or IFN-g is a dimerized soluble cytokine which is a Type II Interferon. ...
A bacteriocide or bactericide is a substance that kills bacteria and, preferably, nothing else. ...
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. ...
Interleukin-4, abbreviated IL-4, is a Cytokine that stimulates the proliferation of activated B-cells, T-cells, and differentiation of CD4+T-cells into Th2 cells, among other effects. ...
Humoral immunity is the aspect of immunity that is mediated by secreted antibodies, produced in the cells of the B lymphocyte lineage (B cell). ...
In cell biology, molecular biology and related fields, the word intracellular means inside the cell. It is used in contrast to extracellular (outside the cell). ...
In cell biology, molecular biology and related fields, the word extracellular means outside the cell. It is used in contrast to intracellular (inside the cell). ...
The venom of the black widow spider is a potent latrotoxin. ...
HIV is able to subvert the immune system by attacking the CD4+ T cells, precisely the cells that could drive the destruction of the virus, but also the cells that drive immunity against all other pathogens encountered during an organisms' lifetime.[3] Human immunodeficiency virus or HIV is a retrovirus that causes Acquired Immunodeficiency Syndrome (AIDS), a condition in which the immune system begins to fail, leading to life-threatening opportunistic infections. ...
A third type of T lymphocyte, the regulatory T cells (Treg), limits and suppresses the immune system, and may control aberrant immune responses to self-antigens; an important mechanism in controlling the development of autoimmune diseases.[3] This article or section should be merged with suppressor T cell Regulatory T cells (also known as suppressor T cells) are characterised by virtue of their expression of the cell surface markers CD4 and CD25. ...
Immune or immunological tolerance is the process by which the immune system does not attack an antigen. ...
B lymphocytes and antibody production -
 The B lymphocyte activation pathway. B cells function to protect the host by producing antibodies that identify and neutralize foreign objects like bacteria and viruses. [4] B Cells are the major cells involved in the creation of antibodies that circulate in blood plasma and lymph, known as humoral immunity. Antibodies (or immunoglobulin, Ig), are large Y-shaped proteins used by the immune system to identify and neutralize foreign objects. In mammals there are five types of antibody: IgA, IgD, IgE, IgG, and IgM, differing in biological properties, each has evolved to handle different kinds of antigens. Upon activation, B cells produce antibodies, each of which recognizes a unique antigen, and neutralize specific pathogens.[1] B cells are lymphocytes that play a large role in the humoral immune response (as opposed to the cell-mediated immune response). ...
Image File history File links Download high-resolution version (665x1000, 348 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Immune system ...
Image File history File links Download high-resolution version (665x1000, 348 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Immune system ...
Wikipedia does not yet have an article with this exact name. ...
Blood plasma is the liquid component of blood, in which the blood cells are suspended. ...
Humoral immunity is the aspect of immunity that is mediated by secreted antibodies, produced in the cells of the B lymphocyte lineage (B cell). ...
IGA may stand for: Koji Igarashi, a video game producer Interactive genetic algorithm International Geothermal Association Independent Glass Association International Gothic Association International Gamers Award International Goat Association Irish Games Association Irish Geological Association ImmunoGlobulin A - see IgA nephritis which is a renal disease IGA (supermarkets) Independent Grocers Association or...
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. ...
IGE (Internet Gaming Entertainment) is a MMORPG services company. ...
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 complex used by the immune system to identify and neutralize foreign objects like bacteria and viruses. ...
Like the T cell receptor, B cells express a unique B cell receptor (BCR), in this case, an immobilized antibody molecule. The BCR recognizes and binds to only one particular antigen. A critical difference between B cells and T cells is how each cell "sees" an antigen. T cells recognize their cognate antigen in a processed form - as a peptide in the context of an MHC molecule,[1] while B cells recognize antigens in their native form.[1] Once a B cell encounters its cognate (or specific) antigen (and receives additional signals from a helper T cell (predominately Th2 type)), it further differentiates into an effector cell, known as a plasma cell.[1] 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). ...
Differentiation can mean the following: In biology: cellular differentiation; evolutionary differentiation; In mathematics: see: derivative In cosmogony: planetary differentiation Differentiation (geology); Differentiation (logic); Differentiation (marketing). ...
Plasma cells are short lived cells (2-3 days) which secrete antibodies. These antibodies bind to antigens, making them easier targets for phagocytes, and trigger the complement cascade.[1] About 10% of plasma cells will survive to become long-lived antigen specific memory B cells.[1] Already primed to produce specific antibodies, these cells can be called upon to respond quickly if the same pathogen re-infects the host; while the host experiences few, if any, symptoms.
Plasma cells are B lymphocytes that secrete immunoglobulins (antibodies). ...
Memory B cells are a B cell sub-type that are formed following primary infection. ...
Immunological memory & diversity Most large molecules, including virtually all proteins and many polysaccharides, can serve as antigens.[1] The parts of an antigen that interact with an antibody molecule or a lymphocyte receptor, are called epitopes. Most antigens contain a variety of epitopes and can stimulate the production of antibodies, specific T cell responses, or both.[1] A representation of the 3D structure of myoglobin, showing coloured alpha helices. ...
Polysaccharides (sometimes called glycans) are relatively complex carbohydrates. ...
An epitope is the part of a macromolecule that is recognized by the immune system, specifically by antibodies, B cells, or cytotoxic T cells. ...
 An antibody is made up of two heavy chains and two light chains. The unique variable region allows an antibody to recognize its matching antigen. [4] A very small proportion (less than 0.01%) of the total lymphocytes are able to bind to a particular antigen, which suggests that only a few cells will respond to each antigen.[3] Image File history File links Antibody. ...
Image File history File links Antibody. ...
For the adaptive response to "remember" and eliminate a large number of pathogens the immune system must be able to distinguish between many different antigens,[2] and the receptors that recognize antigens must be produced in a huge variety of configurations, essentially one receptor for each different pathogen that might ever be encountered. Even in the absence of antigen stimulation, a human is capable of producing more than 1 trillion different antibody molecules[3]. Millions of genes would be required to store the genetic information used to produce these receptors, but, the entire human genome contains fewer than 50,000 genes.[2] So, how are so many antibodies and antigen receptors produced? This stylistic schematic diagram shows a gene in relation to the double helix structure of DNA and to a chromosome (right). ...
This myriad of receptors are produced through a process known as clonal selection.[1][2] According to the clonal selection theory, at birth, an animal will randomly generate a vast diversity of lymphocytes (each bearing a unique antigen receptor) from information encoded in a small family of genes. In order to generate each unique antigen receptor, these genes will have undergone a process called combinatorial diversification, in which one gene segment recombines with other gene segments to form a single unique gene. It is this assembly process that generates the enormous diversity of receptors and antibodies, before the body ever encounters antigens, and enables the immune system to respond to an almost unlimited diversity of antigens[1]. Throughout the lifetime of an animal, those lymphocytes that can react against the antigens an animal actually encounters, will be selected for action, directed against anything that expresses that antigen. The clonal selection theory has become a widely accepted model for how the immune system responds to infection and how certain types of B and T lymphocytes are selected for destruction of specific antigens invading the body. ...
It is important to note that the innate and adaptive portions of the immune system work together and not in spite of each other. The adaptive arm, B and T cells, would be unable to function without the input of the innate system. T cells are useless without antigen-presenting cells to activate them, and B cells are crippled without T-cell help. On the other hand, the innate system would likely be overrun with pathogens without the specialized action of the adaptive immune response.
Adaptive immunity during pregnancy The cornerstone of the immune system is the recognition of “self” versus “non-self”. Therefore, the mechanisms which protect the human fetus (which is clearly not “self”) from attack by the immune system, are particularly interesting. Although no comprehensive explanation has emerged to explain this mysterious, and often repeated, lack of rejection, two classical reasons may explain how the fetus is tolerated. The first is that the fetus occupies a portion of the body protected by a non-immunological barrier, the uterus, which the immune system does not routinely patrol.[1] The second is that the fetus itself may promote local immunosuppression in the mother, perhaps by a process of active nutrient depletion.[1] A more modern explanation for this induction of tolerance is that specific glycoproteins expressed in the uterus during pregnancy suppress the uterine immune response (see eu-FEDS). Fetus at eight weeks For other uses, see Fetus (disambiguation). ...
The uterus or womb is the major female reproductive organ of most mammals, including humans. ...
A pregnant woman near the end of her term Pregnancy is the carrying of one or more embryos or fetuses by female mammals, including humans, inside their bodies. ...
The Eutherian Fetoembryonic Defense System, also known by the acronym eu-FEDS is a hypothetical model describing a specific type of immunological tolerance that occurs during reproduction in mammals[1] Eutherians are members of the taxon Eutheria, which encompasses all mammals with a true placenta. ...
See also Image File history File links Commons-logo. ...
Wikimedia Commons logo by Reid Beels The Wikimedia Commons (also called Commons or Wikicommons) is a repository of free content images, sound and other multimedia files. ...
The process by which B-cells produce antibodies with increased affinity for antigen. ...
To meet Wikipedias quality standards, this article or section may require cleanup. ...
Immunosuppression is the medical suppression of the immune system. ...
This article needs to be cleaned up to conform to a higher standard of quality. ...
V(D)J recombination is a mechanism of DNA recombination used by humans and other vertebrates for protection against attacks by bacterial, viral, and parasitic invaders. ...
References - ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa Janeway, Charles, Paul Travers, Mark Walport, and Mark Shlomchik (2001). Immunobiology; Fifth Edition. New York and London: Garland Science. ISBN 0815341016..
- ^ a b c d e Alberts, Bruce, Alexander Johnson, Julian Lewis, Martin Raff, Keith Roberts, and Peter Walters (2002). Molecular Biology of the Cell; Fourth Edition. New York and London: Garland Science. ISBN 0815332181.
- ^ a b c d e f g h i Janeway CA, Jr. et al (2005). Immunobiology., 6th ed., Garland Science. ISBN 0-443-07310-4.
- ^ a b c d e The NIAID resource booklet "Understanding the Immune System (pdf)".
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