Name of the Test:

C3a des Arg

Alias Names:

Complement 3a des arg, Complement 3a

Clinical Applications:

Complement activation is associated with sepsis, respiratory distress syndrome, multi-organ failure, and transplant organ rejection. C3 is the most abundant protein of the complement system and predominantly synthesized by hepatocytes. C3 can be cleaved in two divalent fragments, where C3b is the larger fragment. C3a is the smaller fragment that is released into the surrounding fluids. C3a can bind to receptors on basophils and mast cells triggering them to release their vasoactive amines (e.g. histamine). Because of the role of these biomarkers in anaphylaxis, C3a is called an anaphylatoxin. C3a is one of the most potent constrictors of smooth muscle cells. C3a has been shown to be a multifunctional pro-inflammatory mediator. Complement C3a was found to be elevated in patients with inflammation, autoimmune diseases, chronic hepatitis C, and HCV-related hepatitis cell carcinoma. An inherited deficiency of C3 predisposes patients to frequent bouts of bacterial infections.


C3a des Arg is formed in the blood and plasma, from C3a via carboxypeptidase cleavage of the C-terminal arginine group. C3a is short lived in blood and plasma samples. Hence, the quantitation of C3a des Arg is more reliable measurement of C3a in plasma specimens. A long term study of liver and other transplant recipients for both C3a des Arg and C4a des Arg may be useful in assessing a number of pathological conditions related to inflammatory processes.



C3a des Arg is quantitated using an immunometric enzyme assay using two antibodies, specific to C3a (sandwich assay).  Microtiter plates were coated with monoclonal anti-C3a des Arg and incubated with samples containing C3a and C3a des Arg. The trapped antigen is detected using HRP conjugated polyclonal anti –C3a. The color developed by enzyme reaction is proportional to C3a des Arg concentration.


Test information:

Specimen requirements:  1.0 ml ( minimum 0.2 ml ) of Plasma ( EDTA ). Serum samples are acceptable if they are collected and frozen immediately or collected with protease inhibitors, such as Futhan. Ship the samples frozen or in ice pack. Shipping samples at room temperature is not recommended.

Turnaround time:  1 day ( Set up every Monday  and report the same day).

Reference range:  Adults ( EDTA plasma )  : Less than 780 ng /ml.

In a study with 25 normal serum samples, the concentration of C3a des Arg were less than 4000 ng /ml .


1.Zillow G, Sturm JA, Rother U, Kirschfink M ( 1990) Complement activation and the prognostic value of C3a in patients at risk of adult respiratory distress syndrome. Clin Exp Immunol 79 : 151 -157.

2.Moxley G, Ruddy S ( 1987) Elevated plasma C3 anaphylatoxin levels in rheumatoid arthritis patients. Arthritis Rheum 30: 1097 – 104.

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