Complement receptor
A complement receptor is a membrane-bound receptor belonging to the complement system, which is part of the innate immune system. Complement receptors bind effector protein fragments that are produced in response to antigen-antibody complexes or damage-associated molecules.[1] Complement receptor activation contributes to the regulation of inflammation, leukocyte extravasation, and phagocytosis; it also contributes to the adaptive immune response.[2][3] Different complement receptors can participate in either the classical complement pathway, the alternative complement pathway, or both.[4] Expression and functionWhite blood cells, particularly monocytes and macrophages, express complement receptors on their surface. 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. Red blood cells (RBCs) also express CR1, which enables RBCs to carry complement-bound antigen-antibody complexes to the liver and spleen for degradation.[5]
Clinical significanceDeficits in complement receptor expression can cause disease.[6] Mutations in complement receptors which alter receptor function can also increase risk of certain diseases.[1] See alsoReferences
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