Search results
Results from the WOW.Com Content Network
Scheme of the complement system. The complement system, also known as complement cascade, is a part of the humoral, innate immune system and 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. [1]
The classical and alternative complement pathways. C3b is the larger of two elements formed by the cleavage of complement component 3, and is considered an important part of the innate immune system. C3b is potent in opsonization: tagging pathogens, immune complexes (antigen-antibody), and apoptotic cells for phagocytosis.
The classical pathway is distinct from the other complement pathways in its unique activation triggers and cascade sequence. Activation of the complement pathway through the classical, lectin or alternative complement pathway is followed by a cascade of reactions eventually leading to the membrane attack complex.
All four complement receptors can bind to fragments of complement component 3 or complement component 4 coated on pathogen surface, but the receptors trigger different downstream activities. [1] Complement receptor (CR) 1, 3, and 4 function as opsonins which stimulate phagocytosis, whereas CR2 is expressed only on B cells as a co-receptor.
In both cases C1q activates complement, resulting in the cells being marked for phagocytosis by C3b and C4b. C1q is an important contributor to the clearance of apoptotic cells and debris. This process usually occurs in late apoptotic cells. [6] Opsonization of apoptotic cells occurs by different mechanisms in a tissue-dependent pattern.
The classical and alternative complement pathways. Complement-pathways. C3 convertase (C4bC2b, formerly C4b2a) 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.
The alternative pathway is a type of cascade reaction of the complement system and is a component of the innate immune system, a natural defense against infections. The alternative pathway is one of three complement pathways that opsonize and kill pathogens. The pathway is triggered when the C3b protein directly binds a microbe. It can also be ...
Phagoptosis is normally caused by: the cell exposing on its surface so-called "eat-me" signals, and/or the cell no longer exposing "don't-eat-me" signals and/or the cell being opsonised i.e. binding soluble proteins that tag the cell for phagocytosis. For example, phosphatidylserine is an "eat-me" signal that, when exposed on the surface of a ...