CD8A and chronic myelogenous leukemia, BCR-ABL1 positive: In addition, the higher expression of PD-1 on peripheral CD8+ T cells detected in all the patients treated with TKI, especially for TKI-F patients, this consistent with recent research that a higher percentage of PD-1 detected on CD4+, CD8+ and Treg cells in CML patients resistant to TKI (33), however, on the level of T cell subsets, we can see that the percentage of PD-1 high expression T cell subsets mainly decreased in the patients who achieved MMR but not in TKI-F and Pre-MMR patients.