Both CD4+ and CD8+ T cells in CML BM express high levels of putative exhaustion markers such as PD-1, T cell immunoglobulin mucin-3 (TIM3), and cytotoxic T lymphocyte associated antigen 4 (CTLA-4)15. Here, CTLA4 is linked to chronic myelogenous leukemia, BCR-ABL1 positive.