Macrophage-1 antigen
Encyclopedia
Macrophage-1 antigen is a complement receptor
("CR3") consisting of CD11b and CD18
.
It binds to C3b
and C4b.
, capable of recognizing and binding to many molecules found on the surfaces of invading bacteria. CR3 also recognizes iC3b
when bound to the surface of foreign cells. Binding to the receptor causes phagocytosis and destruction of the foreign cell.
CR3 belongs to a family of cell surface receptors known as integrin
s (because they share this particular β chain, they are referred to as β2-integrins), which are extremely widely distributed throughout nature and which generally are important in cellular adhesion and cell-cell interactions in a variety of cells and circumstances.
Upregulation of MAC-1 in the presence of certain factors such as Il-2 may cause a prolongation of the life of the immune cell while the presence of TNF-alpha induces apoptosis and selective removal of the cell.
A fully activated neutrophil may express on its membrane 200,000 or more CR3 molecules.
Absence of CR3 results in reduced binding and ingestion of Mycobacterium tuberculosis (in mice).
Complement receptor
A complement receptor is a receptor of the complement system, a part of the mediated innate immune system. Complement receptors are responsible for detecting pathogens by mechanisms not mediated by antibodies. Complement activity is not antigen sensitive, but can be triggered by specific antigens...
("CR3") consisting of CD11b and CD18
CD18
Integrin beta-2 is a protein that in humans is encoded by the ITGB2 gene.It is the beta subunit of four different structures:* LFA-1 * Macrophage-1 antigen * Integrin alphaXbeta2...
.
It binds to C3b
C3b
C3b is the larger of two elements formed by the cleavage of complement component 3. C3b covalently bonds to microbial cell surfaces within an organism's body. This leads to the production of surface-bound C3 convertase and thus more C3b components. Bound C3b also aids in opsonization of the microbe...
and C4b.
Function
Complement receptor 3 (CR3)(CD11b/CD18) is a human cell surface receptor found on polymorphonuclear leukocytes (mostly neutrophils), NK cells, and mononuclear phagocytes like macrophages. CR3 is a pattern recognition receptorPattern recognition receptor
Pattern recognition receptors are a primitive part of the immune system. They are proteins expressed by cells of the innate immune system to identify pathogen-associated molecular patterns , which are associated with microbial pathogens or cellular stress, as well as damage-associated molecular...
, capable of recognizing and binding to many molecules found on the surfaces of invading bacteria. CR3 also recognizes iC3b
Complement system
The complement system helps or “complements” the ability of antibodies and phagocytic cells to clear pathogens from an organism. It is part of the immune system called the innate immune system that is not adaptable and does not change over the course of an individual's lifetime...
when bound to the surface of foreign cells. Binding to the receptor causes phagocytosis and destruction of the foreign cell.
CR3 belongs to a family of cell surface receptors known as integrin
Integrin
Integrins are receptors that mediate attachment between a cell and the tissues surrounding it, which may be other cells or the ECM. They also play a role in cell signaling and thereby regulate cellular shape, motility, and the cell cycle....
s (because they share this particular β chain, they are referred to as β2-integrins), which are extremely widely distributed throughout nature and which generally are important in cellular adhesion and cell-cell interactions in a variety of cells and circumstances.
Upregulation of MAC-1 in the presence of certain factors such as Il-2 may cause a prolongation of the life of the immune cell while the presence of TNF-alpha induces apoptosis and selective removal of the cell.
A fully activated neutrophil may express on its membrane 200,000 or more CR3 molecules.
Absence of CR3 results in reduced binding and ingestion of Mycobacterium tuberculosis (in mice).