P-GLYCOPROTEIN EXPRESSION IN ACUTE MYELOBLASTIC-LEUKEMIA ANALYZED BY IMMUNOCYTOCHEMISTRY AND FLOW-CYTOMETRY

Using the APAAP technique, we assessed the reactivity of five monoclon al antibodies, JSB1, C219, Mab 57, 2F8 and MRK16, to gp 170 in 60 case s of de novo acute myeloid leukemia (AML) and 13 relapses. Reactivity, varied between the five antibodies, and positivity was obtained with 2F8 > JSB1 > MRK16 > Mab57 > C219. Sixteen of the 60 cases were also s tudied by flow cytometry. In 10 cases, the results with the two techni ques corresponded, in the other 6 cases, flow cytometry proved more se nsitive than APAAP in detecting small amounts of gp170. In the flow cy tometry analysis, the cells fixed in methanol and paraformaldehyde wer e more fluorescent than unfixed samples or those fixed in paraformalde hyde or methanol alone. Our results thus reveal that positivity for gp 170 depends on various factors, including the specificity of the mono clonal antibodies, the techniques used and the preservation of the sam ples. This suggests the need for a dear standardization of the methods to detect gp170.