Myelodysplastic syndrome patients display alterations in their immune status reflected by increased PD‐L1‐expressing stem cells and highly dynamic exhausted T‐cell frequencies

Summary Little data are available for the expression of immune checkpoint (IC) molecules within myelodysplastic syndrome (MDS). Here, we report increased PD‐L1+CD34+CD38− and PD‐L1+CD34+CD38+ stem cell frequencies within MDS patients compared to stem cell recipients in remission. Additionally, we observed exceedingly similar PD1+ and Tim‐3+ T‐cell frequencies between acute myeloid leukaemia (AML) and MDS samples that were elevated compared to patients in remission. Furthermore, we found highly dynamic Tim‐3+ and PD1+ T‐cell frequencies within serial samples of relapsing MDS with excess blasts (MDS‐EB II) patients, correlating with further disease markers. These findings support the idea of a potential successful implementation of IC inhibitor treatment in suitable MDS patients.