Calibrator 28 is a lyophilized blend of ICOS, LIGHT/TNFSF14, MMP-1, MMP-7, Nectin-4, Perforin, and VEGFR-1/Flt-1. It is intended for use as an assay calibrator for MSD U-PLEX human 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. ICOS, LIGHT/TNFSF14, MMP-1, MMP-7, and Nectin-4 were produced in a mouse cell line; Perforin was expressed in a human cell line; VEGFR-1/Flt-3 was expressed in an insect cell line. Instructions on using Calibrator 28 are provided in U-PLEX Immuno-Oncology Group 1 Human Product Inserts.