OBJECTIVETo investigate the immunophenotype of leukemia promyelocytes (LP) in bone marrow of patients with acute promyelocytic leukemia (APL) and to explore their characteristics and significance.

METHODSThe immunophenotypes of leukemia cells in 43 patients with APL were analyzed by means of 4 color immunophenotypes; the cell population in which CD45 strength localized at 10(2) and the SSC strength locatized at 10(2) was defined as R3, the cell population in which CD45 strength localized at 10(3) and the SSC strength localized at 10(2) was defined as R5, moreover the ratio of positive cells >80% was defined as strong positive expression, the ratio of positive cells between 20%-80% was difined as weak positive expression, the ratio of positive cells <20% was difined as negative by gating method of CD45/SSC.

RESULTSThere was a abnormal cell population (R3) in 79.07% cases; the immunophenotypes of R3 was cheracteried by high SSC, weaker expression of CD45, the rate of CD38, CD9 and CD13 all was 100%, moreover their bright expression (>80%) was 86.05%, 90.70% and 86.05%, respectively; the positive expression rate of CD33, CD117 and CD64 was 97.67%, 95.35% and 83.80% respectively, moreover thier bright expression was 84.04%, 69.77% and 30.23% respectively; the CD15 was weakly expressed in 39.53% cases, the CD34 and HLA-DR were weakly expression in 16.28% and 6.98% cases respectively. All the cases did not express CD116. There were 2 cell populations (R3 and R5) in 20.93% cases, the immunophenotypic features of R3 were cosistant with above mentioning, while the immunophenotypes of R5 were lower than those of R3 SSC; the fluorescence intensity of CD45 was higher, but lower than that in normal lymphycytes, the positive rate of CD9, CD13, MPO was 100%, moreover thier fluorescence intensity was high; they did not expressed CD123, CD25, CD22, CD4, CD64 and CD14. Thereby it can be concluded that the typical immunophenotypes is characterized by CD13(+) CD9(+) CD38(+) CD33(+) CD117(+) CD64(+) CD11b(-) CD34(-) HLA-DR(-) in APL. There was a special immunophenotype in the APL with basophilic granules. Conclusoin: APL has a characteristic immunophenotypic profile, whose typical immunophenotype is characterized by CD13(+) CD9(+) CD38(+) CD33(+) CD117(+) CD64(+) CD11b(-) CD34(-) HLA-DR(-). The special immunophenotype exists in the APL with basophilic granules. Flow cytometric immunophenotyping may be a useful for rapid recognition of APL and has significant for prognosis.