Advanced Diagnostic Laboratories

C1 Function

Test Code

C1F

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 C1 hemolytic assay is a sensitive method for detection of the classical complement activation protein complex C1 (C1q, C1r2, C1s2) activity or lack thereof. Severe or recurrent infections that produce strong activation of the classical complement pathway can lead to low C1 protein levels and reduced C1 activity. Low or absent C1 activity is also observed with genetic deficiencies of C1q, C1r and/or C1s that lead to a lack of or insufficient production of these proteins. Low C1 activity can be associated with low CH50 activity.

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