Discovery and characterization of mHAg HEATR1: Pretransplantation cells from donor and recipient are used to generate an HLA-B8–restricted hematopoiesis-specific CD8 T-cell clone (J47). This clone was used to identify the parent gene of the mHAg as HEATR1. One peptide candidate from this gene, ISKERAEAL, was recognized by J47. The allele in the donor was found to differ by one amino acid.