C3 (complement component 3) is a central glycoprotein in the complement system that serves multiple critical functions in immune defense and inflammation. C3 is the most abundant complement protein in plasma and is essential to all three complement activation pathways (classical, lectin, and alternative), serving as the convergence point where all pathways merge 1. The protein functions as a multifunctional molecule that interacts with numerous serum proteins, cell surface receptors, and membrane-associated regulatory proteins, playing important roles in immune response, opsonization and phagocytosis of pathogens, and immune complex solubilization 2. C3 is primarily synthesized in the liver but also produced extrahepatically in various tissues including glomerular epithelial cells, mesangial cells, and astrocytes 345. Its expression is regulated by inflammatory mediators, with interferon-gamma enhancing C3 gene expression in glomerular epithelial cells and astroglioma cells 35, while insulin downregulates C3 expression in hepatocytes through PPARγ activation 6. C3 deficiency, caused by various genetic mutations including splicing defects and amino acid substitutions, results in increased susceptibility to infections and immune dysfunction 2. The complement system's main outputs include lytic killing of microbes, release of pro-inflammatory anaphylatoxins, and opsonization of targets 1.