HAVCR2 and myelodysplastic syndrome: Increased malignant clones and cellular immunodeficiency might contribute to the pathogenesis of MDS.1, 2, 3, 4, 5 Cytotoxic T lymphocytes (CTLs) play a central role in tumour immunity.6 Adoptive T cell immunotherapy in neoplastic disorders has been restricted by CD8+ T cells ‘exhaustion’ due to some immune checkpoint inhibitors, such as T cell immunoglobulin and mucin domain 3 (TIM3), programmed death‐1 (PD‐1), cytotoxic T lymphocyte antigen 4 (CTLA‐4) and lymphocyte‐activation gene 3 (LAG3).7, 8