Related Research Articles
The complement system, also known as complement cascade, is a part of the immune system that enhances (complements) the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, promote inflammation, and attack the pathogen's cell membrane. It is part of the innate immune system, which is not adaptable and does not change during an individual's lifetime. The complement system can, however, be recruited and brought into action by antibodies generated by the adaptive immune system.
The classical complement pathway is one of three pathways which activate the complement system, which is part of the immune system. The classical complement pathway is initiated by antigen-antibody complexes with the antibody isotypes IgG and IgM.
C3 convertase belongs to family of serine proteases and is necessary in innate immunity as a part of the complement system which eventuate in opsonisation of particles, release of inflammatory peptides, C5 convertase formation and cell lysis.
Pattern recognition receptors (PRRs) play a crucial role in the proper function of the innate immune system. PRRs are germline-encoded host sensors, which detect molecules typical for the pathogens. They are proteins expressed, mainly, by cells of the innate immune system, such as dendritic cells, macrophages, monocytes, neutrophils and epithelial cells, to identify two classes of molecules: pathogen-associated molecular patterns (PAMPs), which are associated with microbial pathogens, and damage-associated molecular patterns (DAMPs), which are associated with components of host's cells that are released during cell damage or death. They are also called primitive pattern recognition receptors because they evolved before other parts of the immune system, particularly before adaptive immunity. PRRs also mediate the initiation of antigen-specific adaptive immune response and release of inflammatory cytokines.
The lectin pathway or lectin complement pathway is a type of cascade reaction in the complement system, similar in structure to the classical complement pathway, in that, after activation, it proceeds through the action of C4 and C2 to produce activated complement proteins further down the cascade. In contrast to the classical complement pathway, the lectin pathway does not recognize an antibody bound to its target. The lectin pathway starts with mannose-binding lectin (MBL) or ficolin binding to certain sugars.
Complement C1r subcomponent is a protein involved in the complement system of the innate immune system. In humans, C1r is encoded by the C1R gene.
Complement component 1s is a protein involved in the complement system. C1s is part of the C1 complex. In humans, it is encoded by the C1S gene.
Mannan-binding lectin serine protease 1 also known as mannose-associated serine protease 1 (MASP-1) is an enzyme that in humans is encoded by the MASP1 gene.
Mannan-binding lectin serine protease 2 also known as mannose-binding protein-associated serine protease 2 (MASP-2) is an enzyme that in humans is encoded by the MASP2 gene.
Mannose-binding protein-associated serine protease are serine proteases involved in the complement system.
Factor D is a protein which in humans is encoded by the CFD gene. Factor D is involved in the alternative complement pathway of the complement system where it cleaves factor B.
Collectins (collagen-containing C-type lectins) are a part of the innate immune system. They form a family of collagenous Ca2+-dependent defense lectins, which are found in animals. Collectins are soluble pattern recognition receptors (PRRs). Their function is to bind to oligosaccharide structure or lipids that are on the surface of microorganisms. Like other PRRs they bind pathogen-associated molecular patterns (PAMPs) and danger-associated molecular patterns (DAMPs) of oligosaccharide origin. Binding of collectins to microorganisms may trigger elimination of microorganisms by aggregation, complement activation, opsonization, activation of phagocytosis, or inhibition of microbial growth. Other functions of collectins are modulation of inflammatory, allergic responses, adaptive immune system and clearance of apoptotic cells.
Mannose-binding lectin (MBL), also called mannan-binding lectin or mannan-binding protein (MBP), is a lectin that is instrumental in innate immunity as an opsonin and via the lectin pathway.
Anti-Saccharomyces cerevisiae antibodies (ASCAs) are antibodies against antigens presented by the cell wall of the yeast Saccharomyces cerevisiae. These antibodies are directed against oligomannose sequences α-1,3 Man n. ASCAs and perinuclear antineutrophil cytoplasmic antibodies (pANCAs) are the two most useful and often discriminating biomarkers for colitis. ASCA tends to recognize Crohn's disease more frequently, whereas pANCA tend to recognize ulcerative colitis.
Complement C1q subcomponent subunit A is a protein that in humans is encoded by the C1QA gene.
Ficolin-1, and also commonly termed M-ficolin is a protein that in humans is encoded by the FCN1 gene.
C3a is one of the proteins formed by the cleavage of complement component 3; the other is C3b. C3a is a 77 residue anaphylatoxin that binds to the C3a receptor (C3aR), a class A G protein-coupled receptor. It plays a large role in the immune response.
CUB domain is an evolutionarily conserved protein domain. The CUB domain is a structural motif of approximately 110 residues found almost exclusively in extracellular and plasma membrane-associated proteins, many of which are developmentally regulated. These proteins are involved in a diverse range of functions, including complement activation, developmental patterning, tissue repair, axon guidance and angiogenesis, cell signalling, fertilisation, haemostasis, inflammation, neurotransmission, receptor-mediated endocytosis, and tumour suppression. Many CUB-containing proteins are peptidases belonging to MEROPS peptidase families M12A (astacin) and S1A (chymotrypsin).
Mannose-binding lectin-associated protein of 44 kDa (MAp44) is a protein arising from the human MASP1 gene. MASP-1, MASP-3 and MAp44 are alternative splice products of the MASP1 gene. MAp44 has been suggested to act as a competitive inhibitor of lectin pathway activation, by displacing MASP-2 from MBL, hence preventing cleavage of C4 and C2
Ficolins are pattern recognition receptors that bind to acetyl groups present in the carbohydrates of bacterial surfaces and mediate activation of the lectin pathway of the complement cascade.
References
- ↑ Matsushita M, Fujita T (December 1992). "Activation of the classical complement pathway by mannose-binding protein in association with a novel C1s-like serine protease". The Journal of Experimental Medicine. 176 (6): 1497–502. doi:10.1084/jem.176.6.1497. PMC 2119445 . PMID 1460414.
- ↑ Thiel S, Vorup-Jensen T, Stover CM, Schwaeble W, Laursen SB, Poulsen K, Willis AC, Eggleton P, Hansen S, Holmskov U, Reid KB, Jensenius JC (April 1997). "A second serine protease associated with mannan-binding lectin that activates complement". Nature. 386 (6624): 506–10. doi:10.1038/386506a0. PMID 9087411.
- ↑ Rossi V, Cseh S, Bally I, Thielens NM, Jensenius JC, Arlaud GJ (November 2001). "Substrate specificities of recombinant mannan-binding lectin-associated serine proteases-1 and -2". The Journal of Biological Chemistry. 276 (44): 40880–7. doi: 10.1074/jbc.M105934200 . PMID 11527969.
- ↑ Ambrus G, Gál P, Kojima M, Szilágyi K, Balczer J, Antal J, Gráf L, Laich A, Moffatt BE, Schwaeble W, Sim RB, Závodszky P (February 2003). "Natural substrates and inhibitors of mannan-binding lectin-associated serine protease-1 and -2: a study on recombinant catalytic fragments". Journal of Immunology. 170 (3): 1374–82. doi: 10.4049/jimmunol.170.3.1374 . PMID 12538697.
- ↑ Harmat V, Gál P, Kardos J, Szilágyi K, Ambrus G, Végh B, Náray-Szabó G, Závodszky P (October 2004). "The structure of MBL-associated serine protease-2 reveals that identical substrate specificities of C1s and MASP-2 are realized through different sets of enzyme-substrate interactions". Journal of Molecular Biology. 342 (5): 1533–46. doi:10.1016/j.jmb.2004.07.014. PMID 15364579.
- ↑ Chen CB, Wallis R (June 2004). "Two mechanisms for mannose-binding protein modulation of the activity of its associated serine proteases". The Journal of Biological Chemistry. 279 (25): 26058–65. doi: 10.1074/jbc.M401318200 . PMID 15060079.
- ↑ Teillet F, Dublet B, Andrieu JP, Gaboriaud C, Arlaud GJ, Thielens NM (March 2005). "The two major oligomeric forms of human mannan-binding lectin: chemical characterization, carbohydrate-binding properties, and interaction with MBL-associated serine proteases". Journal of Immunology. 174 (5): 2870–7. doi: 10.4049/jimmunol.174.5.2870 . PMID 15728497.
