Service Providers for Complement 4 (C4)
Complement 4 (C4) is a protein in the complement system, which is part of the body's immune defense against pathogens. The C4 test measures the level of this protein in the blood, which can help assess the activity of the immune system. Low levels of C4 can be seen in conditions such as systemic lupus erythematosus (SLE), rheumatoid arthritis, and glomerulonephritis, where the complement system is often activated inappropriately. Elevated levels of C4 can occur in acute inflammation or liver disease. The C4 test is typically used alongside C3 and other immune system tests to help diagnose autoimmune diseases, monitor disease progression, and evaluate the effectiveness of treatments.