S100A9 and myelodysplastic syndrome: S100A9 and CD33 ligand/receptor pair interactions recruit components to the immunoreceptor tyrosine-based inhibition motif (ITIM) finally resulting in secretion of suppressive IL-10 and TGFβ1.28 Work based on fresh PB and BM samples from MDS patients confirmed the secretion of these 2 cytokines by MDSCs, but interestingly, this secretion was higher in PMN-MDSCs than in M-MDSCs.31 In fact, PMN-MDSC subset dominated the MDSC-expansion in high-risk patients.