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Adaptive Immunity In Jawless Fish
Agnatha, Jawless vertebrates, which today consist entirely of lampreys and hagfish, have an adaptive immune system similar to that found in Gnathostomata, jawed vertebrates. The cells of the agnathan AIS have roles roughly equivalent to those of B cell, B-cells and T cell, T-cells, with three lymphocyte lineages identified so far: *VLRA (most similar to T cell, α/β T cells, in its role and pathway of differentiation) *VLRB (most similar to B cells) *VLRC (most similar to gamma/delta T cells, γ/δ T cells) VLRA and VLRB were identified in 2009, while VLRC was discovered in 2013. Instead of immunoglobulins, they use variable lymphocyte receptors. Antigen receptors Jawless vertebrates do not have Immunoglobulin superfamily, immunoglobulins (Igs), the key proteins to B-cells and T-cells. However, they do possess a system of leucine-rich repeat (LRR) proteins that make up variable lymphocyte receptors (VLRs). This system can produce roughly the same number of potential receptors t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Agnatha
Agnatha (, Ancient Greek 'without jaws') is an infraphylum of jawless fish in the phylum Chordata, subphylum Vertebrata, consisting of both present (cyclostomes) and extinct ( conodonts and ostracoderms) species. Among recent animals, cyclostomes are sister to all vertebrates with jaws, known as gnathostomes. Recent molecular data, both from rRNA and from mtDNA as well as embryological data, strongly supports the hypothesis that living agnathans, the cyclostomes, are monophyletic. The oldest fossil agnathans appeared in the Cambrian, and two groups still survive today: the lampreys and the hagfish, comprising about 120 species in total. Hagfish are considered members of the subphylum Vertebrata, because they secondarily lost vertebrae; before this event was inferred from molecular and developmental data, the group Craniata was created by Linnaeus (and is still sometimes used as a strictly morphological descriptor) to reference hagfish plus vertebrates. While a few scie ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Immunoglobulin Superfamily
The immunoglobulin superfamily (IgSF) is a large protein superfamily of cell surface and soluble proteins that are involved in the recognition, binding, or adhesion processes of cells. Molecules are categorized as members of this superfamily based on shared structural features with immunoglobulins (also known as antibodies); they all possess a domain known as an immunoglobulin domain or fold. Members of the IgSF include cell surface antigen receptors, co-receptors and co-stimulatory molecules of the immune system, molecules involved in antigen presentation to lymphocytes, cell adhesion molecules, certain cytokine receptors and intracellular muscle proteins. They are commonly associated with roles in the immune system. Otherwise, the sperm-specific protein IZUMO1, a member of the immunoglobulin superfamily, has also been identified as the only sperm membrane protein essential for sperm-egg fusion. Immunoglobulin domains Proteins of the IgSF possess a structural domain known as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cytidine Deaminase
Cytidine deaminase is an enzyme that in humans is encoded by the ''CDA'' gene. This gene encodes an enzyme involved in pyrimidine salvaging. The encoded protein forms a homotetramer that catalyzes the irreversible hydrolytic deamination of cytidine and deoxycytidine to uridine and deoxyuridine, respectively. It is one of several deaminases responsible for maintaining the cellular pyrimidine pool. Mutations in this gene are associated with decreased sensitivity to the cytosine nucleoside analogue cytosine arabinoside used in the treatment of certain childhood leukemias. Most cytidine deaminases act on RNA, and the few that act on DNA require ssDNA. A related activation-induced (cytidine) deaminase (AID) regulates antibody diversification, especially the process of somatic hypermutation Somatic hypermutation (or SHM) is a cellular mechanism by which the immune system adapts to the new foreign elements that confront it (e.g. microbes), as seen during class switching. A major co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gene
In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a basic unit of heredity and the molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protein-coding genes and noncoding genes. During gene expression, the DNA is first copied into RNA. The RNA can be directly functional or be the intermediate template for a protein that performs a function. The transmission of genes to an organism's offspring is the basis of the inheritance of phenotypic traits. These genes make up different DNA sequences called genotypes. Genotypes along with environmental and developmental factors determine what the phenotypes will be. Most biological traits are under the influence of polygenes (many different genes) as well as gen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Recombination-activating Gene
The recombination-activating genes (RAGs) encode parts of a protein complex that plays important roles in the rearrangement and recombination of the genes encoding immunoglobulin and T cell receptor molecules. There are two recombination-activating genes RAG1 and RAG2, whose cellular expression is restricted to lymphocytes during their developmental stages. The enzymes encoded by these genes, RAG-1 and RAG-2, are essential to the generation of mature B cells and T cells, two types of lymphocyte that are crucial components of the adaptive immune system. Function In the vertebrate immune system, each antibody is customized to attack one particular antigen (foreign proteins and carbohydrates) without attacking the body itself. The human genome has at most 30,000 genes, and yet it generates millions of different antibodies, which allows it to be able to respond to invasion from millions of different antigens. The immune system generates this diversity of antibodies by shuffling, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Variable Lymphocyte Receptor
Variable lymphocyte receptors (VLRs) belong to the Leucine-rich repeat (LRR) family and mediate adaptive immune responses in the jawless vertebrates, lampreys and hagfish. See also * Adaptive immunity in jawless fish Agnatha, Jawless vertebrates, which today consist entirely of lampreys and hagfish, have an adaptive immune system similar to that found in Gnathostomata, jawed vertebrates. The cells of the agnathan AIS have roles roughly equivalent to those of B ... References {{Reflist Receptors Agnatha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Leucine-rich Repeat
A leucine-rich repeat (LRR) is a protein structural motif that forms an α/β horseshoe fold. It is composed of repeating 20–30 amino acid stretches that are unusually rich in the hydrophobic amino acid leucine. These tandem repeats commonly fold together to form a solenoid protein domain, termed leucine-rich repeat domain. Typically, each repeat unit has beta strand- turn-alpha helix structure, and the assembled domain, composed of many such repeats, has a horseshoe shape with an interior parallel beta sheet and an exterior array of helices. One face of the beta sheet and one side of the helix array are exposed to solvent and are therefore dominated by hydrophilic residues. The region between the helices and sheets is the protein's hydrophobic core and is tightly sterically packed with leucine residues. Leucine-rich repeats are frequently involved in the formation of protein–protein interactions. Examples Leucine-rich repeat motifs have been identified in a large numbe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, responding to stimuli, providing structure to cells and organisms, and transporting molecules from one location to another. Proteins differ from one another primarily in their sequence of amino acids, which is dictated by the nucleotide sequence of their genes, and which usually results in protein folding into a specific 3D structure that determines its activity. A linear chain of amino acid residues is called a polypeptide. A protein contains at least one long polypeptide. Short polypeptides, containing less than 20–30 residues, are rarely considered to be proteins and are commonly called peptides. The individual amino acid residues are bonded together by peptide bonds and adjacent amino acid residues. The sequence of amino acid residue ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gamma/delta T Cells
Gamma delta T cells (γδ T cells) are T cells that have a γδ T-cell receptor (TCR) on their surface. Most T cells are αβ (alpha beta) T cells with TCR composed of two glycoprotein chains called α (alpha) and β (beta) TCR chains. In contrast, γδ T cells have a TCR that is made up of one γ (gamma) chain and one δ (delta) chain. This group of T cells is usually less common than αβ T cells, but are at their highest abundance in the gut mucosa, within a population of lymphocytes known as intraepithelial lymphocytes (IELs). The antigenic molecules that activate gamma delta T cells are still largely unknown. However, γδ T cells are peculiar in that they do not seem to require antigen processing and major histocompatibility complex, major-histocompatibility-complex (MHC) presentation of peptide epitopes, although some recognize MHC class I, MHC class Ib molecules. γδ T cells are believed to have a prominent role in recognition of lipid antigens. They are of an invariant nat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lamprey
Lampreys (sometimes inaccurately called lamprey eels) are an ancient extant lineage of jawless fish of the order Petromyzontiformes , placed in the superclass Cyclostomata. The adult lamprey may be characterized by a toothed, funnel-like sucking mouth. The common name "lamprey" is probably derived from Latin , which may mean "stone licker" ( "to lick" + "stone"), though the etymology is uncertain. ''Lamprey'' is sometimes seen for the plural form. There are about 38 known extant species of lampreys and five known extinct species. Parasitic carnivorous species are the most well-known, and feed by boring into the flesh of other fish to suck their blood; but only 18 species of lampreys engage in this micropredatory lifestyle. Of the 18 carnivorous species, nine migrate from saltwater to freshwater to breed (some of them also have freshwater populations), and nine live exclusively in freshwater. All non-carnivorous forms are freshwater species. Adults of the non-carnivorous ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lymphocyte
A lymphocyte is a type of white blood cell (leukocyte) in the immune system of most vertebrates. Lymphocytes include natural killer cells (which function in cell-mediated, cytotoxic innate immunity), T cells (for cell-mediated, cytotoxic adaptive immunity), and B cells (for humoral, antibody-driven adaptive immunity). They are the main type of cell found in lymph, which prompted the name "lymphocyte". Lymphocytes make up between 18% and 42% of circulating white blood cells. Types The three major types of lymphocyte are T cells, B cells and natural killer (NK) cells. Lymphocytes can be identified by their large nucleus. T cells and B cells T cells (thymus cells) and B cells ( bone marrow- or bursa-derived cells) are the major cellular components of the adaptive immune response. T cells are involved in cell-mediated immunity, whereas B cells are primarily responsible for humoral immunity (relating to antibodies). The function of T cells and B cells is to recognize sp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
T Cell
A T cell is a type of lymphocyte. T cells are one of the important white blood cells of the immune system and play a central role in the adaptive immune response. T cells can be distinguished from other lymphocytes by the presence of a T-cell receptor (TCR) on their cell surface. T cells are born from hematopoietic stem cells, found in the bone marrow. Developing T cells then migrate to the thymus gland to develop (or mature). T cells derive their name from the thymus. After migration to the thymus, the precursor cells mature into several distinct types of T cells. T cell differentiation also continues after they have left the thymus. Groups of specific, differentiated T cell subtypes have a variety of important functions in controlling and shaping the immune response. One of these functions is immune-mediated cell death, and it is carried out by two major subtypes: CD8+ "killer" and CD4+ "helper" T cells. (These are named for the presence of the cell surface proteins CD8 or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
