Background: Important insight into leukemic differentiation and the cellular origin of acute leukemia have been gained through the use of monoclonal antibodies that define cell surface antigens.
Methods: Using flow cytometry, leukemic blasts from 67 children with acute lymphoblastic leukemia(ALL) were typed with immunologic cell surface markers using monoclonal antibodies according to the classification by Foon and Todd(Blood 68:1-31), 1986 from October 1990 to July 1992. These studies have been supplemented with other markers such as cytoplasmic immunoglobulin on B lymphocytes and terminal
deoxynucleotidyl transferase.
Results: Among 67 patients with ALL in children, 51 cases with non-T-ALL were divided into the group 1 in one patient(1.5%), group 2 in 6(9.0%), group 3 in 33 (49.3%), group 4 in 6(9.0%), and group 5 in 5(7.5%), but none in group 6. T-ALL was divided into the groups of early thymocyte in 6 patients(9.0%), common thymocyte in 6 patients(9.0%) and mature thymocyte in 2 patients(3.0%). In 2 patients with biphenotype, one had the surface markers of T-ALL(CD2+, CD5+ and CD7+) and ANLL(My7+ and My9+), and the other had those of non-T-ALL(DR+, CD19+ and CALLA-) and ANLL(My9+).
T-ALL was found more frequently in high risk group with male sex, age above 10 year-old, lymphadenopathy, mediastinal mass, higher leukocyte count, and/or higher
hemoglobin level than these of non-T-ALL.
Conclusion: With above results, we can confirm the fact that immunophenotyping using flow cytometry was very effective in the diagnosis and subclassification of ALL.

Keywords: Monoclonal Antibodies, Acute Lymphoblastic Leukemia, Flow Cytometry, Immuno-phenotyping, Biphenotype,