OBJECTIVETo explore the diagnostic value of intracellular antibody combination in acute leukemia (AL) expressing cross-lineage cell-surface antigens.

METHODSFlow cytometric immunophenotyping using intracellular antibody combination (cMPO/cCD79alpha/cCD3/CD45) was performed additionally in 60 patients who expressed cross-lineage antigens from 269 previously untreated adult AL.

RESULTSFifty-four of 269 previously untreated adult AL patients who expressed only one kind of intracellular antigen were diagnosed as cross-lineage AL, the percentage of cross-lineage AL in T cell acute lymphoblastic leukemia (T-ALL), B-ALL and acute myeloid leukemia (AML) was 28.6%, 43.6% and 13.4%, respectively. The positive rate of CD7, CD19, CD5 and CD20 in cross-lineage AML was 65.4%, 15.4%, 11.5%, and 7.7%, respectively. The positive rate of CD13, CD33 and CD15 in cross-lineage ALL was 89.3%, 21.4% and 3.6%, respectively. Six (2.3%) patients expressed two-lineage intracellular antigens were diagnosed as biphenotypic AL: 2 of T/B type and 4 B/M (B/myeloid) type.

CONCLUSIONIntracellular antibodies possess lineage specificity and four-color combination flow cytometric immunophenotyping can provide fast and multi-parameter data. To ensure accuracy of the results, CD45/SSC gating and normal cells as internal reference should be used in the immunophenotyping of abnormal cells.