Abstract: Objective To observe the expressions of CD7 in adult acute myelocytic leukemia(AML) and further establish a flow cytometric method for minimal residual disease(MRD) detection.Methods 112 adult patients with AML enrolled in this study.The four-color flow cytometry was used to analyze the characteristics of AML phenotypes.The three or four color fluorochrome labeled monoclonal antibody combinations of CD7 with other myeloid markers,such as CD13,CD33 or CD117,were used to detect MRD.Results 34 of 112 adult patients with CD7⁺ AML were investigated;they were classified into the following subgroups according to French-American-British(FAB) classification: 1 case M₁,26 cases M₂,2 cases M₃ and 5 cases M₄/M₅.Leukemia cells from all the patients were negative for cytoplasmic CD3 and CD79a.There was no difference between CD7⁺ and CD7^- AML patients in terms of sex and age.A strong correlation between CD7 and CD34 expression was also observed and 91.2% CD7⁺ AML cases co-expressed the CD34 antigen.In the MRD detection of CD7⁺ AML,CD7,combined with other myeloid markers,could effectively distinguish normal cells from leukemia cells in the dual-parameter dot plots.Conclusion CD7 expression could be detected in all the FAB subtypes of adult AML and the total positive percentage was 30.4%.The strong correlation between CD7 and CD34 expression suggested the CD7⁺ AML might be derived from a more immature malignant clone.The combination of CD7 and other myeloid markers could be applied to monitor the MRD and significantly improve the detection sensitivity in adult AML.

Key words: acute myelocytic leukemia, minimal residual disease, CD7, flow cytometry