The correlation analysis incorporating only MDS patients showed strong positive association between the level of PD-1L positive blast cells, the overall level of CD117+CD34+HLA-DRlow blasts (r = 0.80, p<0.0001), PD-1LG2 blasts (r = 0.43, p<0.0001), blasts with ICOS ligand (r = 0.44, p<0.0001), blasts with PD-1 receptor (r = 0.53, p<0.0001), overall pool of HLA-DR cells with PD-1L expression (r = 0.38, p = 0.0003), galectin-9-postive blasts (r = 0.53, p<0.0001). Here, ICOS is linked to myelodysplastic syndrome.