Description
Complement component 3, often simply called C3, is a protein of the immune system. It plays a central role in the complement system and contributes to innate immunity. In humans it is encoded on chromosome 19 by a gene called C3.Decreased C3 may be associated with acute glomerulonephritis, membranoproliferative glomerulonephritis, immune complex disease, active systemic lupus erythematosis, and generalized autoimmune processes.C3 plays a central role in the activation of the complement system. Its activation is required for both classical and alternative complement activation pathways. People with C3 deficiency are susceptible to bacterial infection.In humans, C3 is predominantly synthesised by liver hepatocytes and to some degree by epidermis keratinocytes.Levels of C3 in the blood may be measured to support or refute a particular medical diagnosis. For example, low C3 levels are associated with Systemic Lupus Erythematosus (SLE) and some types of kidney disease such as post-infectious glomerulonephritis, membranoproliferative glomerulonephritis, and shunt nephritis.Deficiencies in C3 lead to genetic infections, usually fatal to the newborn.
Complement C3 is a blood test that measures the activity of a certain protein.C3 comprises about 70% of the total protein in the complement system and is central to activation of both the classical and alternate pathways.In cases of disseminated intravascular coagulation, plasmin attacks C3 directly, and C3 levels have been found low in the hemolytic uremic syndrome form of disseminated intravascular coagulation (DIC). Cases of hereditary C3 deficiency, while rare, have been reported and are characterized clinically by recurrent infections (eg, pneumonia, meningitis, paronychia, impetigo).
Pathogenic bacteria causing infections in these cases have included both gram-positive and gram-negative organisms. C3 levels have also been found deficient in cases of uremia, chronic liver diseases, anorexia nervosa, and celiac disease.In cases of disseminated intravascular coagulation, plasmin attacks C3 directly, and C3 levels have been found low in the hemolytic uremic syndrome form of disseminated intravascular coagulation (DIC). Cases of hereditary C3 deficiency, while rare, have been reported and are characterized clinically by recurrent infections (eg, pneumonia, meningitis, paronychia, impetigo).
This protein is part of the complement system. The complement system is a group of nearly 60 proteins that are in blood plasma or on the surface of some cells. The proteins work with your immune system and play a role to protect the body from infections, and to remove dead cells and foreign material. Rarely, people may inherit deficiency of some complement proteins. These people are prone to certain infections or autoimmune disorders.There are nine major complement proteins. They are labeled C1 through C9. C3 and C4 are the most commonly measured complement components.A complement test may be used to monitor people with an autoimmune disorder. It is done to see if treatment for their condition is working. When the complement system is turned on during inflammation, levels of complement proteins may go down. For example, people with active lupus erythematosus may have lower-than-normal levels of the complement proteins C3 and C4.Complement activity varies throughout the body. For example, in people with rheumatoid arthritis, complement activity in the blood may be normal or higher-than-normal, but much lower-than-normal in the joint fluid.
The test may also be done for the following conditions:
Fungal infections
Gram negative septicemia
Parasitic infections, such as malaria
Paroxysmal nocturnal hemoglobinuria (PNH)
Shock
The normal range is 88 to 201 milligrams per deciliter (mg/dL) (0.88 to 2.01 g/L).Unlike other C3 fragments, C3c does not bind to other structures, like pathogens, cell surface (receptors) and other plasma proteins. Therefore, C3c is a stable complement biomarker which will appear in the fluid phase only, without interference of other C3 based products.
