Complement C4

Complement C4 is another protein involved in the complement system, which is part of the body’s immune response. Like C3, it plays a role in identifying and marking foreign invaders for destruction. It is activated during immune responses and assists in triggering inflammation and the destruction of pathogens

The C4 serum test is used to assess the activation of the complement system, and its levels can be altered in various conditions:

• Autoimmune Diseases: Reduced C4 levels are common in autoimmune diseases like systemic lupus erythematosus (SLE).
• Chronic Infections: Infections that persist or are severe may deplete complement proteins like C4.
• Kidney Disease: Certain kidney diseases affect complement activity, including conditions like lupus nephritis.
• Inflammatory Conditions: Conditions causing widespread inflammation can lead to changes in C4 levels.

• Individuals with suspected autoimmune conditions like lupus or rheumatoid arthritis.
• People experiencing persistent, unexplained infections or illnesses.
• Patients with kidney disease, particularly those suspected of having immune-mediated kidney conditions.
• Individuals with unexplained symptoms such as fatigue, joint pain, or skin rashes.

C4 levels are often measured alongside C3 to evaluate the complement system's activity. While low levels of C4 can be seen in autoimmune diseases, normal levels do not rule out such conditions. Elevated C4 levels are less commonly associated with specific conditions but can be seen during acute-phase reactions or infections.