All patients examined had significantly increased surface expression of PD-1 on both CD71+ erythroid progenitors (P < 0.05; Fig. 1a) and CD34+ HSPCs (P < 0.01; Fig. 1b) versus the corresponding healthy donor BM populations, suggesting PD-1 upregulation may play a role in MDS. Here, TFRC is linked to myelodysplastic syndrome.