The assay is For Research Use Only (FRUO). EPO is regarded as the only 100% specific marker of human eosinophils and is not found in any other cell in the human body. Our EPO ELISA is based on monoclonal antibodies produced against EPO purified from human eosinophils. The unavailability of commercial immunoassays for EPO has precluded so far the investigation of the usefulness of this biomarker to reflect eosinophil involvement in human disease. By the launch of our specific and sensitive EPO ELISA we have overcome this problem and look forward to learn more about this exciting new biomarker. Indeed our assay has been used in a recent publication in the prestigious journal, Journal of Clinical Investigation (https://www.jci.org/articles/view/95693).