Immunophenotyping of acute myeloid leukemia using monoclonal antibodies and the alkaline phosphatase-antialkaline phosphatase technique.

The leukemic cells from 41 cases of acute myeloid leukemia (AML) and 17 cases of acute lymphocytic leukemia (ALL) were immunophenotyped by the alkaline phosphatase-antialkaline phosphatase (APAAP) immunocytochemical technique utilizing eight monoclonal antibodies (MoAb) reactive with cells of myeloid origin and seven MoAb reactive with lymphoid antigens. Ninety percent of the cases of AML reacted with one or more of the pan-myeloid MoAb, My7, My9, or 20.3. Reactivity of the myeloid panel of MoAb showed some correlation with the French-American-British (FAB) classification of AML. Five of six cases of acute promyelocytic leukemia (APL) were HLA-DR negative; the one HLA-DR-positive APL had a minor population of HLA-DR-negative promyelocytes. OKM5 and/or My4 reacted with 16 of 16 monocytic leukemias. No specific marker of early erythroid development was identified. AP3, a MoAb reactive with platelet glycoprotein (GPIIIa), was specific for acute megakaryoblastic leukemia. Immunocytochemistry was also helpful in classifying seven cases of AML with equivocal or negative routine cytochemistry. Two cases of AML had minor populations of blasts detected by the APAAP technique that were immunologically distinct from the major blast population; these minor populations emerged as the predominant cell type at relapse. Two cases of ALL expressed multiple myeloid and lymphoid antigens. Two other cases that morphologically were ALL reacted with only myeloid MoAb; one consisted entirely of immature basophils on ultrastructural examination. Immunophenotyping results using the APAAP technique were comparable with those obtained with flow cytometry. The APAAP technique is a reliable method for immunophenotyping leukemia that complements other methods of immunologic evaluation. The primary advantages of this method include its use with routinely prepared blood and bone marrow smears and the ability to correlate immunocytochemical reactions with morphology.