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 ...

These findings suggest complement protein levels may be an important biomarker for type 1 diabetes. Disruption of the complement system appears to precede the onset of islet autoimmunity (IA), making ...

Levels of C4d and C4d/C4 associate with clinical and histopathological treatment response in proliferative lupus nephritis. Complement activation markers, particularly C4d and the C4d/C4 ratio, are ...

A new study published in the journal Science Immunology analyzed lung epithelial cells from patients infected with COVID-19 and found the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) ...