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. Complement receptor activation contributes to the regulation of inflammation, leukocyte extravasation, and phagocytosis; it also contributes to the adaptive immune response. Different complement receptors can participate in either the classical complement pathway, the alternative complement pathway, or both. Expression and function
White 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. 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. a.^ B: B cell. E: erythrocyte. Endo: endothelial cell. D: dendritic cell. FDC: follicular dendritic cell. Mac: macrophage. MC: mast cell. M0: monocyte. Pha: phagocyte. PMN: polymorphonuclear leukocyte. Clinical significance
Deficits in complement receptor expression can cause disease. Mutations in complement receptors which alter receptor function can also increase risk of certain diseases. See also
Complement system
Humoral immunity
Immune system

References
External links
Complement+receptors at the US National Library of Medicine Medical Subject Headings (MeSH)
The antiproliferative effects of moexipril have also been demonstrated by in vitro studies where moexipril inhibits the estrogen-stimulated growth of neonatal cardiac fibroblasts in rats. Other ACE inhibitors have also been found to produce these actions, as well. Pharmacology
Moexipril is available as a prodrug moexipril hydrochloride, and is metabolized in the liver to form the pharmacologically active compound moexiprilat. Formation of moexiprilat is caused by hydrolysis of an ethyl ester group. Moexipril is incompletely absorbed after oral administration, and its bioavailability is low. The long pharmacokinetic half-life and persistent ACE inhibition of moexipril allows once-daily administration.Moexipril is highly lipophilic, and is in the same hydrophobic range as quinapril, benazepril, and ramipril. Lipophilic ACE inhibitors are able to penetrate membranes more readily, thus tissue ACE may be a target in addition to plasma ACE. A significant reduction in tissue ACE (lung, myocardium, aorta, and kidney) activity has been shown after moexipril use.It has additional PDE4-inhibiting effects. Synthesis

The synthesis of the all-important dipeptide-like side chain involves alkylation of the tert-butyl ester of L-alanine (2) with ethyl 2-bromo-4-phenylbutanoate (1); the presominane of the desired isomer is attributable to asymmetric induction from the adjacent chiral center. Reaction of the product with hydrogen chloride then cleaves the tert-butyl group to give the half acid (3). Coupling of that acid to the secondary amine on tetrahydroisoquinoline (4) gives the corresponding amine. The tert-butyl ester in this product is again cleaved with hydrogen chloride to afford moexipril (5). == References ==