PRAME and neoplasm: Because the signature contained mostly intracellular proteins and additional samples from the discovery sets were not available to us, we next used single-cell profiling on T cells sorted and stimulated by the tumor antigen PRAME from a patient who relapsed after HCT compared with T cells sorted and stimulated by the viral antigen cytomegalovirus (CMV) pp65a as a surrogate measurement for an antitumoral response post-HCT.