Calibrator 9 is a lyophilized blend of 10 recombinant human proteins: EPO, FLT3L, IFN-β, IL-3, IL-9, IL-17B, IL-17C, IL-17D, IL-1RA, and IL-2Rα. It is intended for use as an assay calibrator for MSD U-PLEX human and non-human primate assays that measure any of the included proteins. The utility of this product has not been evaluated in other applications. Individual analyte concentrations are provided in the lot-specific certificates of analysis. IL-3, IL-17C, IL-17D, and IL-1RA were expressed in E.coli. FLT3L and IL-9 were expressed in insect cells, EPO, IFN-β, and IL-17B were expressed in Chinese hamster cells, and IL-2Rα was expressed in a mouse cell line. Instructions on using Calibrator 9 are provided in U-PLEX Group 1 Human Product Inserts and U-PLEX Group 1 NHP Product Inserts.