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Immunodominant Epitopes
Immunodominance is the immunological phenomenon in which immune responses are mounted against only a few of the antigenic peptides out of the many produced. That is, despite multiple allelic variations of MHC molecules and multiple peptides presented on antigen presenting cells, the immune response is skewed to only specific combinations of the two. Immunodominance is evident for both antibody-mediated immunity and cell-mediated immunity. Epitopes that are not targeted or targeted to a lower degree during an immune response are known as subdominant epitopes. The impact of immunodominance is immunodomination, where immunodominant epitopes will curtail immune responses against non-dominant epitopes. Antigen-presenting cells such as dendritic cells, can have up to six different types of MHC molecules for antigen presentation. There is a potential for generation of hundreds to thousands of different peptides from the proteins of pathogens. Yet, the effector cell population that is rea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antigen
In immunology, an antigen (Ag) is a molecule, moiety, foreign particulate matter, or an allergen, such as pollen, that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune response. Antigens can be proteins, peptides (amino acid chains), polysaccharides (chains of simple sugars), lipids, or nucleic acids. Antigens exist on normal cells, cancer cells, parasites, viruses, fungus, fungi, and bacteria. Antigens are recognized by antigen receptors, including antibodies and T-cell receptors. Diverse antigen receptors are made by cells of the immune system so that each cell has a specificity for a single antigen. Upon exposure to an antigen, only the lymphocytes that recognize that antigen are activated and expanded, a process known as clonal selection. In most cases, antibodies are ''antigen-specific'', meaning that an antibody can only react to and bind one specific antigen; in some instances, however, antibodies may cr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Major Histocompatibility Complex
The major histocompatibility complex (MHC) is a large Locus (genetics), locus on vertebrate DNA containing a set of closely linked polymorphic genes that code for Cell (biology), cell surface proteins essential for the adaptive immune system. These cell surface proteins are called MHC molecules. Its name comes from its discovery during the study of transplanted tissue compatibility. Later studies revealed that tissue rejection due to incompatibility is only a facet of the full function of MHC molecules, which is to bind an antigen derived from self-proteins, or from pathogens, and bring the antigen presentation to the cell surface for recognition by the appropriate T cell, T-cells. MHC molecules mediate the interactions of leukocytes, also called white blood cells (WBCs), with other leukocytes or with body cells. The MHC determines donor compatibility for organ transplant, as well as one's susceptibility to autoimmune diseases. In a cell, protein molecules of the host's own pheno ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Epitope
An epitope, also known as antigenic determinant, is the part of an antigen that is recognized by the immune system, specifically by antibodies, B cells, or T cells. The part of an antibody that binds to the epitope is called a paratope. Although epitopes are usually non-self proteins, sequences derived from the host that can be recognized (as in the case of autoimmune diseases) are also epitopes. The epitopes of protein antigens are divided into two categories, conformational epitopes and linear epitopes, based on their structure and interaction with the paratope. Conformational and linear epitopes interact with the paratope based on the 3-D conformation adopted by the epitope, which is determined by the surface features of the involved epitope residues and the shape or tertiary structure of other segments of the antigen. A conformational epitope is formed by the 3-D conformation adopted by the interaction of discontiguous amino acid residues. In contrast, a linear epitope i ... [...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] |
T-cell Receptor
The T-cell receptor (TCR) is a protein complex, located on the surface of T cells (also called T lymphocytes). They are responsible for recognizing fragments of antigen as peptides bound to major histocompatibility complex (MHC) molecules. The binding between TCR and antigen peptides is of relatively low affinity and is biologically degenerate (that is, many TCRs recognize the same antigen peptide, and many antigen peptides are recognized by the same TCR). The TCR is composed of two different protein chains (that is, it is a hetero dimer). In humans, in 95% of T cells the TCR consists of an alpha (α) chain and a beta (β) chain (encoded by '' TRA'' and ''TRB'', respectively), whereas in 5% of T cells the TCR consists of gamma and delta (γ/δ) chains (encoded by '' TRG'' and '' TRD'', respectively). This ratio changes during ontogeny and in diseased states (such as leukemia). It also differs between species. Orthologues of the 4 loci have been mapped in various speci ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
B-cell Receptor
The B-cell receptor (BCR) is a transmembrane protein on the surface of a B cell. A B-cell receptor is composed of a membrane-bound immunoglobulin molecule and a signal transduction moiety. The former forms a type 1 Transmembrane protein, transmembrane receptor protein, and is typically located on the Cell membrane, outer surface of these lymphocyte cells. Through biochemical signaling and by physically acquiring antigens from the immune synapses, the BCR controls the activation of the B cell. B cells are able to gather and grab antigens by engaging biochemical modules for receptor clustering, cell spreading, generation of pulling forces, and receptor transport, which eventually culminates in endocytosis and antigen presentation. B cells' mechanical activity adheres to a pattern of negative and positive feedbacks that regulate the quantity of removed antigen by manipulating the dynamic of BCR–antigen bonds directly. Particularly, grouping and spreading increase the relation of anti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antigenic Variation
Antigenic variation or antigenic alteration refers to the mechanism by which an Pathogen, infectious agent such as a protozoan, bacterium or virus alters the proteins or carbohydrates on its surface and thus avoids a host (biology), 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 seque ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
