Platelet-associated TGF-β1 stimulated the function and modulated the transcriptome profiles of MDSCs in active-ITP mice. (A) Platelet counts among the control, Romi, and Romi + TGF-βi groups differed significantly on day 28. (B) Percentage of MDSCs in bone marrow nucleated cells evaluated by FACS. (C) Relative MFI of Arg-1, PD-L1, PD-L2, and iNOS expressed by MDSC from active-ITP mice treated with TGF-βi, Romi, Romi plus TGF-βi, or none. Relative MFI is the fold of average MFI in controls. (D) Serum TGF-β1 level detected by ELISA. Pearson correlation analysis of (E) platelet counts with serum TGF-β1 level and (F) serum TGF-β1 level with MDSC percentage. (G) Gene ontology (GO) enrichment score [−log10(P value)] analysis of DEGs identified between Romi-treated and control mice. (H) KEGG enrichment analysis based on the expression of Romi-altered genes. DEGs, differentially expressed genes; FACS, fluorescence activated cell sorter; KEGG, Kyoto Encyclopedia of Genes and Genomes.