Advanced Diagnostic Laboratories

C4 Function

Test Code

C4F

Description

The complement system is part of our innate immune response. It is vital to our defense against invasive microorganisms. Complement activation can occur through the classical, lectin and alternative pathway, which then converge to a common terminal pathway. Complement deficiency can lead to life-threatening infections as well as long-term autoimmune conditions such as systemic lupus erythematosus (SLE) and hereditary angioedema (HAE).

The C4 hemolytic assay is a sensitive method for detection of classical/lectin complement protein C4 activity or lack thereof. Severe or recurrent infections that produce strong activation of the classical/lectin complement pathway can lead to low C4 protein levels and reduced C4 activity. Low or absent C4 activity is also observed with genetic deficiencies of C4 that lead to a lack of or insufficient production of C4 protein. Low C4 activity can be associated with low CH50 activity.

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