PRTN3 and chronic myelogenous leukemia, BCR-ABL1 positive: To study antigen-specific T cells in CML, we chose PR1, a leukemia-associated antigen from proteinase 3 (PRTN3) and neutrophil elastase (ELANE) genes, as anti-PR1 T cells have been associated with response to TKI [7] and successful IFN-α discontinuation [41].