BACKGROUND: Detection of bcr/abl fusion mRNA using reverse transcription polymerase chain reaction has been used for diagnosis of chronic myelogenous leukemia(CML) and monitoring after treatment. However, this conventional method is not quantitative. Therefore, new quantitative marker for CML is necessary for the follow-up of the patients after treatment including bone marrow transplantation. Whether the lymphocytes are involved in CML clone or not is still a moot question. If the lymphocytes are involved in CML clone, there could be an abnormal surface antigen expressed on these cells. We tried to find out abnormal surface antigen expression on the lymphocytes of CML.
METHODS: We analyzed the immunophenotypic distribution of the bone marrow lymphocytes using flow cytometry in 22 cases of CML and 20 normal persons, and searched for characteristic abnormal immunophenotype of CML. Both peripheral blood and bone marrow samples were analyzed using dual color immunophenotying for CD19 and CD22 expression in 14 cases of CML.
RESULTS: The proportion of lymphocytes with T cell antigen expression and CD10, CD19, CD20 expression were lower in CML than in normal control (P < 0.05). In contrast to these antigens, the proportion of CD22 positive lymphocytes was higher in CML than in normal control (P=0.0434). And loss of correlation between CD19 and CD22 expression was observed in CML. The proportion of CD19-/CD22+ lymphocytes in the bone marrow of 14 cases of CML was higher than that of normal control (P=0.0001). The proportion of CD19-/CD22+ lymphocytes in the peripheral blood of CML was 45.0±22.6%, and higher than 1.0±0.3% of normal control (P=0.0000). The proportion of CD19-/CD22+ lymphocytes in the peripheral blood was higher than that of the bone marrow (P=0.0018). CD22 was not coexpressed with T cell antigens (CD2, CD3) or myeloid antigen (CDl4) in CML or normal control.
CONCLUSION: We demonstrated that the cells, representing unusual immunophenotype of CD19-/CD22+, are characteristically increased in the bone marrow and peripheral blood of CML. This immunophenotype could be a valuable marker for the diagnosis of CML and monitoring after treatment.

Keywords: CML, Lymphocyte, Immunophenotype, CD19-/CD22+