BIPHASIC EXPRESSION OF CD4 IN ACUTE MYELOCYTIC-LEUKEMIA (AML) CELLS -AML OF MONOCYTE ORIGIN AND HEMATOPOIETIC PRECURSOR CELL ORIGIN

In 227 of 495 (45.9%) Japanese adult patients with acute myelocytic le ukemia (AML), leukemic cells expressed CD4. Incidence of CD4 expressio n in each FAB subtype was as follows: M1 37.4%, M2 33.7%, M3 35.4%, M4 65.0%, and U5 78.3%. The typical expression pattern of myelomonocytic differentiation antigens and cytokine receptors in CD4(+) AML was CD3 4(low)CD33(high) CD11b(high)GM-CSFRhigh, AML cases with 11q23 abnormal ities and with inv(16) were frequently CD4-positive. These data collec tively indicate that CD4 expression in AML cells is associated with mo nocytic characteristics. However, CD4(+)CD34(high) AML cases appear to have unique immature characteristics including low expression of myel omonocytic differentiation antigens tie CD33 and CD11b), and accumulat ion of chromosome abnormalities (ie t(8;21) in CD4(low)CD34(high) AM(L ) and chromosome 7 abnormalities in CD4(high)CD34(high) AML). We specu late that these leukemia subsets originate from CD4(+) hematopoietic p recursor cells, therefore then should be considered separately from mo st of the CD4(+) AML as represented by CD34(low)CD33(high) CD11b(high) GM-CSFRhigh. Overall survival of patients with CD4(+) AML in our serie s was worse than that of those with CD4(-) AML (P = 0.0202).