The Tetramer Core serves federally approved investigators throughout the U.S. who require customized tetramer reagents for immunologic studies. Under contract by the National Institute of Allergy and Infectious Diseases, the Tetramer Core develops tetramer reagents that are not available from commercial sources. Tetramers are molecular complexes that can be engineered to bind only to specific types of immune cells – for instance, T-cells that respond to a particular disease-causing agent. Because the tetramers are linked to fluorescent markers, the immune cells of interest can be easily and quickly counted and sorted, thus providing investigators with precise measures of immune response.