Examples of membrane attack complex in the following topics:
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- The end result of this activation cascade is massive amplification of the response and activation of the cell-killing membrane attack complex (also called MAC).
- C5b forms a complex with C6, C7, and then C8, and C9, which becomes the membrane attack complex that lyses the pathogen.
- This factor prevents membrane attack complexes from forming on the body's cells under normal conditions.
- Similarly to the classical pathway, C3b forms a C42b complex, and the rest of the steps are essentially the same as the classical pathway, ending with C5b forming a membrane attack complex with C6, C7, C8, and C9.
- The classical and alternative complement pathways start off differently, but end in the same cascade of complement proteins that combine to form a membrane attack complex.
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- Cytotoxic T cells kill pathogens in several ways, including the release of granules that contain the cytotoxins perforin and granzyme, which lyse small pores in the membrane of a pathogen.
- They also neutralize the toxins produced by certain pathogens and provide complement pathway activation, in which circulating proteins are combined in a complex cascade that forms a membrane attack complex on a pathogen cell membrane, which lyses the cell.
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- The antibodies bind to pathogens to opsonize (mark) them for phagocytes to engulf, neutralize them, or start a complement cascade in which proteins form a membrane attack complex to lyse the pathogen.
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- Using this binding mechanism, an antibody can neutralize its target directly or tag it for attack by other parts of the immune system.
- The complement system starts a long cascade of protein productions that either opsonize a pathogen for phagocytosis or lyse it directly by forming a membrane attack complex.
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- Major histocompatibility complex (MHC) is a cell surface molecule encoded by a large gene family in all vertebrates.
- MHC III- a secreted enzyme that is not membrane bound, nor involved in antigen presenation like MHC I and II.
- Organ transplantation is a complex procedure that can potentially cure many chronic diseases or damaged conditions.
- If the T and B cells of the body recognize the HLA of the graft as foreign, they will attack the organ graft.
- MHC-I/peptide complexes enter Golgi apparatus, are glycosylated, enter secratory vesicles, fuse with the cell membrane, and externalize on the cell membrane interacting with T lymphocytes.
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- Associated disorders: Autoimmune hemolytic anemia, thrombocytopenia, Erythroblastosis, fetalis, Goodpasture's syndrome, Membranous nephropathy, Graves' disease, Myasthenia Gravis.
- Immune Complex Hypersensitivity (Type III) is an immune response to immune complexes (antigen-antibody complexes) that become deposited in a given area.
- This results in continuous localized immune attack (and ensuing tissue damage).
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- However, the different lipoproteins contain apolipoproteins, which serve as ligands for specific receptors on cell membranes.
- Now within the cell, the cholesterol can be used for membrane biosynthesis or esterified and stored within the cell, so as to not interfere with cell membranes.
- These plaques are the main causes of heart attacks, strokes, and other serious medical problems, leading to the association of so-called LDL cholesterol (actually a lipoprotein) with "bad" cholesterol.
- Lipid vesicles (or liposomes) are small, intracellular, membrane-enclosed bubbles of liquid within a cell.
- They are formed because of the properties of lipid membranes, where the hydrophobic chains are packed together so they are not in contact with the aqueous solution.
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- This mechanism allows the immune system to mount stronger attacks each time the pathogen is encountered, thus preparing itself for future challenges and preventing reinfection by the same pathogen.
- An antigen is any
molecule that induces an immune response, such as a toxin or molecular
component of a pathogen cell membrane, and is unique to each species of
pathogen.
- The antigen is processed by the APC and bound to MHC class II receptors and MHC class I receptors on the cell membrane of the APC.
- Cytotoxic cells directly attack cells carrying certain foreign or abnormal molecules on their surfaces.
- In most cases, T cells only recognize an antigen if it is carried on the surface of a cell by one of the body's own MHC, or major histocompatibility complex, molecules.
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- NK cells contain receptors for a molecule called MHC (major histocompatibility complex) class I, which allows the NK cell to distinguish between infected cells and tumors from normal and uninfected cells.
- Normal cells express MHC class I on their cell membranes, while infected or cancerous cells do not express or express reduced amounts of the molecule.
- Activated NK cells release cytotoxic (cell-killing) granules that contain perforin and granzyme, which can lyse (break down) cell membranes and induce apoptosis to kill infected or abnormal cells.
- Sometimes these lymphocytes react to antigens that aren't harmful (allergy) or will attack antigens expressed from the host's own body (autoimmunity).
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- In the absence of ligand, type II nuclear receptors often form a complex with co-repressor proteins.
- The G-protein is bound to the inner membrane of the cell and consists of three sub-units: alpha, beta, and gamma.
- Upon binding to the receptor, it releases a GTP molecule, at which point the alpha sub-unit of the G-protein breaks free from the beta and gamma sub-units and is able to move along the inner membrane until it contacts another membrane-bound protein: the primary effector.
- General schematic of second messenger generation following activation of membrane bound receptors. 1.
- The agonist activates the membrane-bound receptor. 2.