To assess if engagement of PD-1 was also sufficient to provoke hematopoietic progenitor cell death and if this was augmented in MDS, BM-MNC isolated from MDS patients (n = 3) and healthy donors (n = 3) were cultured in plates coated with or without recombinant human PD-L1 for 24 h and levels of activated caspase-3 were determined by flow cytometry. This evidence concerns the gene CASP3 and myelodysplastic syndrome.