Home / Blood Tests / Complement C4

Complement C4

What Is Complement C4?

Complement C4 is a protein that plays a vital role in the body’s immune defence. It is part of the complement system, a network of proteins that assist the immune system in identifying and eliminating pathogens. C4 is produced in the liver and circulates in the bloodstream, ready to be activated in response to infection or inflammation.

Role of Complement C4 in Immune Function

Once activated, C4 contributes to several key immune responses, including:

Opsonisation of pathogens to enhance detection and destruction

Recruitment of immune cells to infection sites

Formation of the membrane attack complex (MAC), which breaks down and destroys targeted cells

These actions are essential for protecting the body from bacteria, viruses, and other harmful agents.

What the Complement C4 Test Measures

A Complement C4 test measures the concentration of C4 protein in the blood. Abnormal levels may indicate underlying health issues and help guide further diagnostic investigations.

Conditions Associated with Abnormal C4 Levels

Low C4 levels are often seen in individuals with autoimmune diseases such as:

Systemic lupus erythematosus (SLE)

Rheumatoid arthritis

High C4 levels may occur in certain infections or inflammatory conditions, including:

Sepsis

Acute-phase inflammatory responses

Factors That May Influence C4 Test Results

Interpretation of Complement C4 levels should be done carefully, as certain medications, such as corticosteroids and immunosuppressants, can alter C4 concentrations. Clinical symptoms and other diagnostic test results must be considered to arrive at an accurate diagnosis.

Complement C4 Testing in Slough and Surrounding Areas

Private testing for Complement C4 is available in Slough, Windsor, Langley, Maidenhead, and neighbouring areas. If you are experiencing symptoms of autoimmune disease or chronic inflammation, local blood testing services in Slough can help detect abnormalities in immune function and guide appropriate medical care.

There is an additional £20 phlebotomy fee for every donation.