Abstract: To explore the role of immunophenotyping in the pathogenesis, diagnosis, classification and differential diagnosis of myelodysplastic syndrome (MDS) and aplastic anemia(AA). MethodsA panel of monoclonal antibodies and flow cytometry using CD45/SSC gating strategies were used for immunophenotyping in bone marrow nucleated cells of 23 patients with MDS, 14 patients with AA and 9 healthy controls. ResultsCompared with the control group, expressions of haemopoietic stem/progenitor cell surface markers CD34 and HLADR, early medullary system surface markers CD13 and CD33, monocyte system surface marker CD14, and T lymphocyte cell surface marker CD7 were significantly increased in the MDS group; however, expressions of later medullary system surface marker CD15, B lymphocyte cell surface markers CD19 and CD20 were significantly decreased in the MDS group（P＜0.05）. However, as RA progressed to RAEB, expressions of CD34, HLADR, CD13, CD33, CD14 and CD7 were significantly increased, while expressions of CD15, CD3, CD19 and CD20 were significantly decreased; and the DI level was significantly increased（P＜0.05）. Expression levels of CD34, CD13, CD33 and CD15 in the AA group were significantly higher than those in the control group and those of CD3, CD7, CD25 and CD22 were lower than those in the control group（P＜0.05）. Also expression levels of CD34, HLADR, CD13, CD33 and CD14 in the MDS group were significantly higher than those in the AA group, while expression levels of CD3, CD5, CD7, CD15, CD19, CD20, CD22 and CD25 were significantly lower in the MDS group than those in the AA group（P＜0.05）. ConclusionImmunophenotyping analysis may be a useful tool for the diagnosis, classification and differential diagnosis of MDS and AA.

Key words: Myelodysplastic syndrome, Anemia,aplastic, Immunophenotyping