Used in immunological research to quantify complement protein C4 levels in biological samples such as serum or plasma. Enables assessment of complement system activation, which is critical in studying autoimmune diseases like lupus, rheumatoid arthritis, and certain kidney disorders. Supports research in monitoring disease progression and evaluating therapeutic interventions targeting the complement pathway. Widely used in clinical laboratories and biomedical research for its sensitivity and specificity in detecting C4 concentration changes.