Used to quantitatively measure human IgG4 levels in biological samples such as serum, plasma, or cell culture supernatants. Commonly applied in clinical research and immunology studies to assess immune responses, monitor autoimmune diseases, and evaluate allergic conditions. Also utilized in therapeutic antibody development where IgG4 isotype antibodies are involved, helping to monitor drug levels or anti-drug antibody responses. The kit enables high-throughput analysis with high specificity and sensitivity, making it suitable for diagnostic laboratories and pharmaceutical research.