C3 nephritis factor (C3Nef) is an IgG-like autoantibody of the alternative pathway C3 convertase (C3b, Bb). C3Nef is combined with C3b and Bb in a ratio of 1:1:1, which can stabilize the enzyme from C3b- Inactivation of INA and B1H, resulting in activation of C3 and other complement components via the alternative pathway. When detecting C3Nef, normal human serum and the test serum are generally co-cultured in the presence of EGTA, such as natural C3 consumption or conversion to C3 cleavage product (C3SP) in normal human serum, indicating that C3Nef exists in the serum to be tested.

Basic Information

Specialist classification: urinary examination classification: immune examination

Applicable gender: whether men and women apply fasting: not fasting

Tips: The detection methods are immunoelectrophoresis and cross immunoelectrophoresis. Normal value

>1028 was positive for C3Nef.

Clinical significance

Membrane proliferative glomerulonephritis, partial lipodystrophy (PL), acute glomerulonephritis, SLE, meningitis, etc. may be positive.


When tube 1 and tube 2 are both single peaks, they are judged to be negative. Tube 1 is bimodal and tube 2 is single peak C3Nef positive. If tube 2 is also a double peak, it may be a false positive caused by natural cleavage of C3 during the test, or it may be due to the presence of C3 cleavage product in the serum to be tested.

Inspection process

Qualitative methods for detecting C 3NeF in serum or plasma of patients include immunoelectrophoresis, cross immunoelectrophoresis, C3 hemolytic activity assay, immunofixation electrophoresis, and sheep erythrocyte hemolysis.

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Adverse reactions and risks

There are no taboos and hazards.