CD33 and myelodysplastic syndrome: For myelodysplastic syndrome (MDS)-MRD positive samples, red cells accounted for 3.36% of nuclear cells in the H gate, expressing CD34, bright CD117, dim CD33, dim HLA-DR, and dim CD200, but not expressing CD4, CD7, CD56, CD13, CD64, CD71, CD38, and CD96, which were malignant myeloid primitive cells (Figure 2b).