SureQuant-MHC utilizes a series of isotopologues and internal standard-triggered targeted mass spectrometry to generate an embedded multipoint calibration curve to determine the endogenous pMHC concentrations for a panel of 18 antigen targets. We apply this methiod to profile changes in pMHC expression levels in melanoma cell lines treated with binimetinib, a MEK inhibitr, and traslate the approach to profiling antigen levels in human tumor punch biopsies.