Keyhole limpet hemocyanin (KLH) is widely used in immunology and biomedical research as a potent carrier protein for haptens, small molecules that are not inherently immunogenic. By conjugating haptens to KLH, researchers can elicit a strong immune response, making it invaluable for antibody production in vaccine development and immunotherapy. KLH is also employed as an immune stimulant in cancer immunotherapy, where it enhances the immune system's ability to target tumor cells. Additionally, it serves as a valuable tool in immunological assays and studies due to its ability to activate T-cells and B-cells, providing insights into immune system mechanisms. Its high molecular weight and stability make it a reliable choice for experimental and therapeutic applications.