Advanced Diagnostic Laboratories

C5 Function

Test Code

C5F

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 C5 hemolytic assay is a sensitive method for detection of complement protein C5 activity or lack thereof. C5 plays a key role in the initiation of the terminal pathway membrane attack complex (MAC). Severe or recurrent infections that produce strong activation of either complement pathway can lead to low C5 protein levels and reduced C5 activity. Low or absent C5 activity is also observed with genetic deficiencies of C5 that lead to a lack of or insufficient production of C5 protein. Low C5 activity can be associated with low CH50 and AH50 activity.

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