Complement C4, Serum

Lower-than-normal complement C4 values could indicate:

- bacterial infections (especially Neisseria)

- hepatitis

- malnutrition

- rejection of a kidney transplant

- systemic lupus erythematosus, which is an autoimmune disease affecting the skin, joints, kidneys, and other organs

- lupus nephritis, which is a kidney disorder that often occurs as a result of systemic lupus erythematosus

- cirrhosis, which indicates significant liver damage

- glomerulonephritis, which is a type of kidney disease

- hereditary angioedema, which is a rare but serious autoimmune disease that causes swelling in various parts of the body

Complement component activity varies throughout the body. People with rheumatoid arthritis, for example, may have high complement levels in their blood but low complement levels in their joint fluid.

Complement C4, a key molecule in the complement system that is one of chief constituents of innate immunity for immediate recognition and elimination of invading microbes, plays an essential role for the functions of both classical (CP) and lectin (LP) complement pathways. Complement C4 is the most polymorphic protein in complement system.

Inflammatory conditions lead to an increase in C4 levels in the blood. The levels of C4 rise with low-grade inflammation. Inflammatory conditions that cause an increase in C4 levels include:

- Obesity, C4 levels increase with BMI
- Skin conditions such as psoriasis, dermatitis, and hives
- Ulcerative colitis and Crohn’s disease
- Psoriatic arthritis and rheumatoid arthritis
- Rheumatic fever
- Inflammation and kidney failure
- Certain types of cancers such as Hodgkin’s lymphoma, leukemia, and sarcoma
- Infection or injury

Levels of C4 are also seen to be elevated during pregnancy and due to use of certain drugs such as cimetidine.

Complement component activity varies throughout the body. People with rheumatoid arthritis, for example, may have high complement levels in their blood but low complement levels in their joint fluid.

Autoimmune diseases involve a lot of factors and may vary from one person to another. It is important to work with your healthcare provider to treat the underlying conditions that may cause your complement levels to be abnormal.

To prevent decrease in the levels of C4, it is advised to refrain from over eating and reducing intake of fatty foods. Supplements such as mangosteen are thought to boost up C4 levels. Avoiding cannabis, exposure to heavy metals and allergens is recommended to avoid C4 levels from going lower than normal.

Certain lifestyle and dietary changes can help reduce the risk of chronic inflammation and prevent the elevation in C4 levels. These changes may include losing weight, exercises, getting enough sleep, reducing stress, consuming an anti-inflammatory diet, etc.