Used in immunological research to quantify levels of CTLA-4 (cytotoxic T-lymphocyte-associated protein 4) in human biological samples such as serum, plasma, or cell culture supernatants. This ELISA kit is particularly valuable in studies related to immune regulation, autoimmune diseases, cancer immunotherapy, and transplant rejection. By measuring soluble or intracellular CTLA-4, researchers can assess T cell activation status and immune checkpoint activity. It supports the development and monitoring of therapies targeting the CTLA-4 pathway, such as immune checkpoint inhibitors. The assay provides a sensitive and specific means to evaluate biomarker expression in clinical and preclinical settings.