C3d Levels, C3 Breakdown Product

Immunology

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Description

C3 forms one of the pivitol components of the complement pathways. When activated it is converted to C3a and C3b. Binding of C3b to a suitable cell membrane allows further complement activation. However if C3b fails to bind effectively it is inactivated (iC3b) by Factor I and other cofactors. Further breakdown products include C3c, C3dg and C3d. Both C3dg and C3d express the complement receptor, CR2, allowing binding with B-cells and dendritic cells [2]. C3d is a useful maker of complement consumption as it is not affected by the acute phase response, unlike C3 which may remain within the normal range despite significant consumption. This test may be clinical useful to determine whether low complement levels indicate active consumption or deficiency. Determining complement consumption can also be used to monitor disease activity in conditions such as SLE Rheumatoid arthritis [1].

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Indications

Differentiation between Complement Deficiency and Consumption. Used to investigate Complement activation/ consumption/ breakdown. Monitoring disease activity in SLE and Rheumatoid arthritis.

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Sample Type

2mL EDTA Plasma (separated in <60 mins).
Requests from outside Sheffield: freeze sample prior to dispatch and transport frozen sample at ambient temperature via Royal Mail or Courier (dry ice not required).

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Reference Range

Normal values <5 mg/L.

Reference range established in house.

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Turnaround Time

Within 4 weeks

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Testing Frequency

As required

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External Notes

Discuss with Clinical Scientists / Medical Staff. Investigation of complement activation and consumption.

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References

PRU Handbook of Clinical Immunochemistry. 9th Ed. 2007. [Ref 1]
Bergmann-Leitner ES, et al. Complement C3d: from molecular adjuvant to target of immune escape mechanisms. Clin Imm. 2006. 121:177-185. [Ref 2]
Sturfelt G and Truedsson L. Complement and its breakdown products in SLE. Rheum. 2005. 44:1227-1232.

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Please note: the above information is subject to change and we endeavour to keep this website up to date wherever necessary.