Diving further into the possible mechanisms of the MDSC-mediated myelodysplasia, P. Cheng et al. reported that elevated levels of S100A9 in the BM of MDS patients may account for the observed increased expression of PD1 and PD-L1 on the HSCs and BM MDSCs, respectively [89]. Here, S100A9 is linked to myelodysplastic syndrome.