Used in immunology research to quantify C1q protein levels in biological samples such as serum, plasma, or cell culture supernatants. Helps assess activation of the classical complement pathway, which plays a key role in immune response, inflammation, and autoimmune diseases like lupus. Enables researchers to study C1q deficiency, immune complex clearance, and its involvement in neurodegenerative conditions and cancer. Suitable for high-throughput screening and biomarker validation in clinical and preclinical studies.