Staging of leukemic progenitor cells in acute myeloid leukemia by phenotyping with myeloid monoclonal antibodies.

We studied the immune phenotype of leukemic progenitor cells (AML-CFU-L) in 16 cases of acute myeloid leukemia (AML) using 12 myeloid monoclonal antibodies (McAbs) in a complement-mediated cytotoxicity assay. On the basis of their reactivities with normal day-14 (D14) and day-7 (D7) myeloid progenitor cells (CFU-GM), these McAbs could be classified into three groups: six McAbs reacted strongly with "early" antigens on D14-CFU-GM, two McAbs reacted only with "late" antigens on D7-CFU-GM, while four McAbs formed an "intermediate" group that reacted both with the "late" antigens on D7-CFU-GM and to some extent with the "early" antigens of D14-CFU-GM. The McAbs all reacted with antigens on AML-CFU-L:McAbs that reacted with "early" antigens reacted consistently strongly with AML-CFU-L, in contrast to McAbs in the two other groups, which displayed greater heterogeneity. On the basis of antigenic phenotype, the predominating CFU-L in AML could thus be placed in one of three "stages." This phenotypic "staging" of AML correlated with the French-American-British (FAB) morphological classification of AML. The AML-CFU-L of patients with FAB morphological types M2, M4, and M5 expressed more differentiated antigenic phenotypes than those of the three patients with M7. The latter reacted poorly with the "intermediate" and "late" McAbs. Our data and those of others suggest that classification based on AML-CFU-L antigenic profile may complement the FAB classification of AML.