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Complement C4

Complement C4 is a protein that is a part of the complement system, a group of proteins that play a critical role in the body's immune response. Complement C4 is synthesized in the liver and can be found in the bloodstream. When activated, C4 can participate in various immune reactions, including the opsonization of foreign particles, the recruitment of immune cells to sites of infection, and the formation of a membrane attack complex (MAC) that can destroy cells. The complement C4 test measures the level of C4 protein in the blood. Abnormal levels of C4 can be indicative of various medical conditions, including autoimmune diseases, such as systemic lupus erythematosus (SLE), and infections, such as sepsis. Low levels of C4 are commonly seen in patients with active SLE, as well as other autoimmune diseases such as rheumatoid arthritis. Elevated levels of C4 can be seen in some types of infections and inflammatory conditions. However, it is important to note that interpretation of the C4 test results must be done in conjunction with other clinical information, and further testing may be necessary to diagnose specific medical conditions. In addition, some medications, such as corticosteroids and immunosuppressants, can affect C4 levels, so it is important to take these into account when interpreting test results.

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