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C4 complement component in blood
Medical expert of the article
Last reviewed: 04.07.2025
Reference values (norm) for C4 content in blood serum are 0.2-0.5 g/l.
C4 is a component of the classical complement activation pathway. It is synthesized in the liver. Determining its content is important for diagnosing immune complex diseases, in which it is adsorbed on immune complexes, which leads to a decrease in the amount of free C4 in the blood.
Changes in C4 concentration in various diseases
Increase in C4 concentration
- Malignant neoplasms, sarcomas, lymphomas
Decreased concentration of C4
- Immune complex diseases
- Systemic lupus erythematosus
- Glomerulonephritis
- Treatment with cytostatics and immunosuppressants
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