S100A9 and myelodysplastic syndrome: IFN-γ, TNF-α, S100A9, PGN and LPS [19, 63, 92], are dysregulated in patients (especially higher in the lower-risk MDS group) [93–96] and could strongly induce PD-L1 upregulation, suggesting a role for PD-L1 in modulating the immune microenvironment.