A complement C4 (also known as a complement component 4, or simply C4) is a test to measure the level of C4 proteins you have in your blood. These proteins play a role in how your immune system ...

Your complement system consists of a group of important proteins in your bloodstream. These proteins help your immune system fight off harmful invaders, such as bacteria, and other foreign substances.

Please provide your email address to receive an email when new articles are posted on . Low complement levels prior to pregnancy are associated with an increased risk for adverse outcomes, including ...

Please provide your email address to receive an email when new articles are posted on . Erythrocyte-bound C4d, a biomarker for systemic lupus erythematosus patented by Exagen Diagnostics, is useful in ...