What complement component is typically decreased in patients during the active stages of systemic lupus erythematosus?

In patients with systemic lupus erythematosus (SLE), complement levels may be altered due to the disease’s impact on the immune system. A hallmark of active SLE is the consumption of complement components, particularly in response to the formation of immune complexes that trigger the complement cascade.

C3, a central component of the complement system, often experiences significant decrease during the active stages of the disease as it is utilized in the inflammatory response and in the opsonization of pathogens and immune complexes. The consumption of C3 frequently reflects increased disease activity, as the body is overwhelmed by the formation of these immune complexes that lead to complement activation. Thus, a low C3 level is commonly found in patients with active SLE, making it a relevant indicator of disease activity.

This understanding is essential not only for diagnosis but also for monitoring disease progression and therapeutic response in patients with systemic lupus erythematosus.