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Negative Selection (immunology)
In immunology, central tolerance (also known as negative selection) is the process of eliminating any ''developing'' T or B lymphocytes that are autoreactive, i.e. reactive to the body itself. Through elimination of autoreactive lymphocytes, tolerance ensures that the immune system does not attack self peptides. Lymphocyte maturation (and central tolerance) occurs in primary lymphoid organs such as the bone marrow and the thymus. In mammals, B cells mature in the bone marrow and T cells mature in the thymus. Central tolerance is not perfect, so peripheral tolerance exists as a secondary mechanism to ensure that T and B cells are not self-reactive once they leave primary lymphoid organs. Peripheral tolerance is distinct from central tolerance in that it occurs once developing immune cells exit primary lymphoid organs (the thymus and bone-marrow), prior to their export into the periphery. Function Central tolerance is essential to proper immune cell functioning because it help ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Immunology
Immunology is a branch of biology and medicine that covers the study of Immune system, immune systems in all Organism, organisms. Immunology charts, measures, and contextualizes the Physiology, physiological functioning of the immune system in states of both health and diseases; malfunctions of the immune system in immunological disorders (such as Autoimmune disease, autoimmune diseases, Hypersensitivity, hypersensitivities, immune deficiency, and transplant rejection); and the physical, chemical, and physiological characteristics of the components of the immune system ''in vitro'', ''In situ#Biology and biomedical engineering, 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 Nob ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Regulatory T Cell
The regulatory T cells (Tregs or Treg cells), formerly known as suppressor T cells, are a subpopulation of T cells that modulate the immune system, maintain immune tolerance, tolerance to self-antigens, and prevent autoimmune disease. Treg cells are immunosuppression, immunosuppressive and generally suppress or downregulation and upregulation, downregulate induction and proliferation of effector T cells. Treg cells express the biomarkers CD4, FOXP3, and CD25 and are thought to be derived from the same cell lineage, lineage as naïve T helper cell, CD4+ cells. Because effector T cells also express CD4 and CD25, Treg cells are very difficult to effectively discern from effector CD4+, making them difficult to study. Research has found that the cytokine Transforming growth factor beta, transforming growth factor beta (TGF-β) is essential for Treg cells to differentiate from naïve CD4+ cells and is important in maintaining Treg cell homeostas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
FEZF1
FEZ family zinc finger 1 is a protein that in humans is encoded by the FEZF1 gene. Clinical significance FEZF1 is a gene that encodes for transcriptional repressors, and it has been shown to repress the transcription factor HES5. In the mouse, FEZF1 is expressed in the forebrain in early development of the embryo. This suppression of HES5 helps to control the differentiation of neural stem cells. FEZF1 also helps to divide the caudal forebrain into three distinct parts during development: the prethalamus, the thalamus, and the pretectum. Mice lacking FEZF1 had no prethalamus and had a smaller thalamus. A loss of function mutation in FEZF1 causes Kallmann Syndrome. As axons are developing and migrating in the early embryo, FEZF1 allows the axons of olfactory neurons to attach to the central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain, spinal cord and retina. The CNS is so named because the brain integr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Autoimmune Regulator
The autoimmune regulator (AIRE) is a protein that in humans is encoded by the ''AIRE'' gene. It is a 13Kilo-base pair, kbp gene on chromosome 21q22.3 that encodes 545 amino acids. AIRE is a transcription factor expressed in the Thymus#Medulla, medulla (inner part) of the thymus. It is part of the Central tolerance, mechanism which eliminates self-reactive T cells that would cause autoimmune disease. It exposes T cells to normal, healthy proteins from all parts of the body, and T cells that react to those proteins are destroyed. Each T cell recognizes a specific antigen when it is presented in complex with a major histocompatibility complex (MHC) molecule by an Antigen-presenting cell, antigen presenting cell. This recognition is accomplished by the T-cell receptor, T cell receptors expressed on the cell surface. T cells receptors are generated by V(D)J recombination, randomly shuffled gene segments which results in a highly diverse population of T cells—each with a unique antig ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
T Helper Cell
The T helper cells (Th cells), also known as CD4+ cells or CD4-positive cells, are a type of T cell that play an important role in the adaptive immune system. They aid the activity of other immune cells by releasing cytokines. They are considered essential in B cell Immunoglobulin class switching, antibody class switching, breaking Cross-presentation, cross-tolerance in dendritic cells, in the activation and growth of cytotoxic T cells, and in maximizing bactericidal activity of phagocytes such as macrophages and neutrophils. CD4+ cells are mature Th cells that express the surface protein CD4. Genetic variation in regulatory elements expressed by CD4+ cells determines susceptibility to a broad class of autoimmune diseases. Structure and function Th cells contain and release cytokines to aid other immune cells. Cytokines are small protein mediators that alter the behavior of target cells that express Receptor (biochemistry), receptors for those cytokines. These cells help polar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cytotoxic T Cell
A cytotoxic T cell (also known as TC, cytotoxic T lymphocyte, CTL, T-killer cell, cytolytic T cell, CD8+ T-cell or killer T cell) is a T lymphocyte (a type of white blood cell) that kills cancer cells, cells that are infected by intracellular pathogens such as viruses or bacteria, or cells that are damaged in other ways. Most cytotoxic T cells express T-cell receptors (TCRs) that can recognize a specific antigen. An antigen is a molecule capable of stimulating an immune response and is often produced by cancer cells, viruses, bacteria or intracellular signals. Antigens inside a cell are bound to class I MHC molecules, and brought to the surface of the cell by the class I MHC molecule, where they can be recognized by the T cell. If the TCR is specific for that antigen, it binds to the complex of the class I MHC molecule and the antigen, and the T cell destroys the cell. In order for the TCR to bind to the class I MHC molecule, the former must be accompanied by a glycoprotei ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RAG1
Recombination activating gene 1 also known as RAG-1 is a protein that in humans is encoded by the ''RAG1'' gene. The RAG1 and RAG2 genes are largely conserved in humans. 55.99% and 55.98% of the encoded amino acids contain no reported variants, respectively. Function The protein encoded by this gene is involved in antibody and T-cell receptor V(D)J recombination. RAG-1 is involved in recognition of the DNA substrate, but stable binding and cleavage activity also requires RAG-2. The RAG-1/2 complex recognizes recombination signal sequences (RSSs) that flank the V, D and J regions in the genes that encode the heavy and light chains of antibodies and components of T-cell receptors. The complex binds to the RSSs and nicks the DNA. This leads to the removal of the intervening DNA and the eventual ligation of the V, D and J sequences. Defects in this gene can cause several different diseases. Clinical significance Because of these effects, Rag1 deletion is used in mouse mod ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Notch Signaling Pathway
The Notch signaling pathway is a highly Conserved sequence, conserved cell signaling system present in most animal, animals. Mammals possess four different Notch proteins, notch receptors, referred to as NOTCH1, NOTCH2, Notch 3, NOTCH3, and NOTCH4. The notch receptor is a single-pass Cell surface receptor, transmembrane receptor protein. It is a hetero-oligomer composed of a large extracellular portion, which associates in a calcium-dependent, non-covalent interaction with a smaller piece of the notch protein composed of a short extracellular region, a single transmembrane-pass, and a small intracellular region. Notch signaling promotes proliferative signaling during neurogenesis, and its activity is inhibited by NUMB (gene), Numb to promote neural differentiation. It plays a major role in the regulation of embryonic development. Notch signaling is dysregulated in many cancers, and faulty notch signaling is implicated in many diseases, including T-cell acute lymphoblastic leuke ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Leukocyte Extravasation
In immunology, leukocyte extravasation (also commonly known as leukocyte adhesion cascade or diapedesis – the passage of cells through the intact vessel wall) is the movement of leukocytes (white blood cells) out of the circulatory system (extravasation) and towards the site of tissue damage or infection. This process forms part of the innate immune response, involving the recruitment of non-specific leukocytes. Monocytes also use this process in the absence of infection or tissue damage during their development into macrophages. Overview Leukocyte extravasation occurs mainly in post-capillary venules, where haemodynamic shear stress, shear forces are minimised. This process can be understood in several steps: # Chemotaxis#Chemoattractants and chemorepellents, Chemoattraction # Rolling adhesion # Tight adhesion # (Endothelial) Transmigration It has been demonstrated that leukocyte recruitment is halted whenever any of these steps is suppressed. White blood cells (leukocytes) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thymus
The thymus (: thymuses or thymi) is a specialized primary lymphoid organ of the immune system. Within the thymus, T cells mature. T cells are critical to the adaptive immune system, where the body adapts to specific foreign invaders. The thymus is located in the upper front part of the chest, in the anterior superior mediastinum, behind the sternum, and in front of the heart. It is made up of two lobes, each consisting of a central medulla and an outer cortex, surrounded by a capsule. The thymus is made up of immature T cells called thymocytes, as well as lining cells called epithelial cells which help the thymocytes develop. T cells that successfully develop react appropriately with Major histocompatibility complex, MHC immune receptors of the body (called ''positive selection'') and not against proteins of the body (called ''negative selection''). The thymus is the largest and most active during the neonatal and pre-adolescent periods. By the early teens, the Thymic involuti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Natural Killer Cell
Natural killer cells, also known as NK cells, are a type of cytotoxic lymphocyte critical to the innate immune system. They are a kind of large granular lymphocytes (LGL), and belong to the rapidly expanding family of known innate lymphoid cells (ILC) and represent 5–20% of all circulating lymphocytes in humans. The role of NK cells is analogous to that of cytotoxic T cells in the vertebrate adaptive immune response. NK cells provide rapid responses to virus-infected cells, stressed cells, tumor cells, and other intracellular pathogens based on signals from several activating and inhibitory receptors. Most immune cells detect the antigen presented on MHC class I, major histocompatibility complex I (MHC-I) on infected cell surfaces, but NK cells can recognize and kill stressed cells in the absence of antibodies and MHC, allowing for a much faster immune reaction. They were named "natural killers" because of the notion that they do not require activation to kill cells that are m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hematopoietic Stem Cell
Hematopoietic stem cells (HSCs) are the stem cells that give rise to other blood cells. This process is called haematopoiesis. In vertebrates, the first definitive HSCs arise from the ventral endothelial wall of the embryonic aorta within the (midgestational) aorta-gonad-mesonephros region, through a process known as endothelial-to-hematopoietic transition. In adults, haematopoiesis occurs in the red bone marrow, in the core of most bones. The red bone marrow is derived from the layer of the embryo called the mesoderm. Haematopoiesis is the process by which all mature blood cells are produced. It must balance enormous production needs (the average person produces more than 500 billion blood cells every day) with the need to regulate the number of each blood cell type in the circulation. In vertebrates, the vast majority of hematopoiesis occurs in the bone marrow and is derived from a limited number of hematopoietic stem cells that are multipotent and capable of extensive ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
